diff --git a/sagemaker-core/src/sagemaker/__init__.py b/sagemaker-core/src/sagemaker/__init__.py
index 71038bb89b..34badfccd5 100644
--- a/sagemaker-core/src/sagemaker/__init__.py
+++ b/sagemaker-core/src/sagemaker/__init__.py
@@ -1,2 +1,16 @@
 """Namespace package for SageMaker."""
-__path__ = __import__('pkgutil').extend_path(__path__, __name__)
+
+__path__ = __import__("pkgutil").extend_path(__path__, __name__)
+
+# Register the fallback finder that gives actionable migration guidance for v2
+# modules removed in v3. Doing it here (in the namespace package init, which
+# runs on any ``import sagemaker.*``) ensures the guidance is active even when a
+# removed module is the very first sagemaker import in the process (e.g.
+# ``import sagemaker.estimator``), before ``sagemaker.core`` is otherwise loaded.
+# Fully guarded so it can never interfere with importing the package.
+try:
+    from sagemaker.core.deprecations import register_removed_module_finder as _register
+
+    _register()
+except Exception:  # pylint: disable=W0703  # noqa: E722
+    pass
diff --git a/sagemaker-core/src/sagemaker/algorithm.py b/sagemaker-core/src/sagemaker/algorithm.py
new file mode 100644
index 0000000000..d1bfdcb444
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/algorithm.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.algorithm`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.algorithm",
+    replacement="`ModelTrainer`",
+    v3_import="from sagemaker.train import ModelTrainer",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.train.model_trainer.html",
+)
diff --git a/sagemaker-core/src/sagemaker/automl.py b/sagemaker-core/src/sagemaker/automl.py
new file mode 100644
index 0000000000..509e46d839
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/automl.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.automl`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.automl",
+    replacement="the `AutoMLJob` resource",
+    v3_import="from sagemaker.core.resources import AutoMLJob",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/src/sagemaker/base_predictor.py b/sagemaker-core/src/sagemaker/base_predictor.py
new file mode 100644
index 0000000000..fb01410a23
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/base_predictor.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.base_predictor`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.base_predictor",
+    replacement="the `Endpoint` resource",
+    v3_import="from sagemaker.core.resources import Endpoint",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/src/sagemaker/core/__init__.py b/sagemaker-core/src/sagemaker/core/__init__.py
index 498c85390a..ad6225aa63 100644
--- a/sagemaker-core/src/sagemaker/core/__init__.py
+++ b/sagemaker-core/src/sagemaker/core/__init__.py
@@ -1,9 +1,17 @@
 """SageMaker Core package for low-level resource management and SDK foundations."""
+
 from sagemaker.core.utils.utils import enable_textual_rich_console_and_traceback
+from sagemaker.core.deprecations import register_removed_module_finder
 
 
 enable_textual_rich_console_and_traceback()
 
+# Install the fallback finder that gives actionable migration guidance for v2
+# modules removed in v3 but not individually tombstoned. sagemaker-core is the
+# universal dependency of every v3 package, so registering here guarantees the
+# finder is active whenever the SDK is used.
+register_removed_module_finder()
+
 # Job management
 from sagemaker.core.job import _Job  # noqa: F401
 from sagemaker.core.processing import (  # noqa: F401
diff --git a/sagemaker-core/src/sagemaker/core/deprecations.py b/sagemaker-core/src/sagemaker/core/deprecations.py
index a8ba298082..38500ad6f3 100644
--- a/sagemaker-core/src/sagemaker/core/deprecations.py
+++ b/sagemaker-core/src/sagemaker/core/deprecations.py
@@ -13,13 +13,236 @@
 """Module for deprecation abstractions."""
 from __future__ import absolute_import
 
+import importlib.abc
 import logging
+import sys
 import warnings
 
 logger = logging.getLogger(__name__)
 
 V2_URL = "https://sagemaker.readthedocs.io/en/stable/v2.html"
 
+# Migration guide for users moving from the v2 SDK to v3.
+V3_MIGRATION_URL = "https://github.com/aws/sagemaker-python-sdk/blob/master/migration.md"
+
+# Real top-level ``sagemaker.*`` names that ship in v3. The fallback finder must
+# never intercept these -- even when a package (e.g. sagemaker-train) is simply
+# not installed, its absence should surface the normal error, not a bogus
+# "removed in v3" message.
+_KNOWN_V3_TOPLEVEL = frozenset({"core", "train", "serve", "mlops", "lineage", "ai_registry"})
+
+# Top-level ``sagemaker.<name>`` modules that existed in v2 but were removed in
+# v3 (some relocated under ``sagemaker.core.*``). Derived from the v2 top-level
+# module surface (the ``master-v2`` branch), minus names that still exist in v3.
+# The fallback finder only emits migration guidance for THESE names, so a typo
+# or hallucinated import (e.g. ``sagemaker.foobar``) gets a plain
+# ``ModuleNotFoundError`` rather than a misleading "was removed" message. V2 is
+# in maintenance, so this surface is effectively frozen.
+_REMOVED_V2_MODULES = frozenset(
+    {
+        "_studio",
+        "accept_types",
+        "algorithm",
+        "amazon",
+        "amtviz",
+        "analytics",
+        "apiutils",
+        "async_inference",
+        "automl",
+        "aws_batch",
+        "base_deserializers",
+        "base_predictor",
+        "base_serializers",
+        "batch_inference",
+        "chainer",
+        "clarify",
+        "cli",
+        "collection",
+        "compute_resource_requirements",
+        "config",
+        "container_base_model",
+        "content_types",
+        "dataset_definition",
+        "debugger",
+        "deprecations",
+        "deserializers",
+        "djl_inference",
+        "drift_check_baselines",
+        "enums",
+        "environment_variables",
+        "estimator",
+        "exceptions",
+        "experiments",
+        "explainer",
+        "feature_store",
+        "fw_utils",
+        "git_utils",
+        "huggingface",
+        "hyperparameters",
+        "image_uri_config",
+        "image_uris",
+        "inference_recommender",
+        "inputs",
+        "instance_group",
+        "instance_types",
+        "instance_types_gpu_info",
+        "interactive_apps",
+        "iterators",
+        "job",
+        "jumpstart",
+        "lambda_helper",
+        "local",
+        "logs",
+        "metadata_properties",
+        "metric_definitions",
+        "mlflow",
+        "model",
+        "model_card",
+        "model_life_cycle",
+        "model_metrics",
+        "model_monitor",
+        "model_uris",
+        "modules",
+        "multidatamodel",
+        "mxnet",
+        "network",
+        "parameter",
+        "partner_app",
+        "payloads",
+        "pipeline",
+        "predictor",
+        "predictor_async",
+        "processing",
+        "pytorch",
+        "remote_function",
+        "resource_requirements",
+        "rl",
+        "s3",
+        "s3_utils",
+        "script_uris",
+        "serializer_utils",
+        "serializers",
+        "serverless",
+        "session",
+        "session_settings",
+        "sklearn",
+        "spark",
+        "sparkml",
+        "stabilityai",
+        "telemetry",
+        "tensorflow",
+        "training_compiler",
+        "transformer",
+        "tuner",
+        "user_agent",
+        "utilities",
+        "utils",
+        "vpc_utils",
+        "workflow",
+        "wrangler",
+        "xgboost",
+    }
+)
+
+
+def raise_removed_in_v3(module, replacement=None, v3_import=None, v3_docs=None):
+    """Warn and then raise an actionable error for a v2 module removed in v3.
+
+    The v2 SDK exposed top-level modules (e.g. ``sagemaker.estimator``) that no
+    longer exist in v3. Importing one would otherwise fail with a bare
+    ``ModuleNotFoundError: No module named 'sagemaker.estimator'`` that gives the
+    caller no path forward. This helper is called from lightweight "tombstone"
+    modules that stand in for those removed names: it emits a
+    ``DeprecationWarning`` and then raises a ``ModuleNotFoundError`` whose message
+    names the exact v3 replacement, the import to copy-paste, and a direct link
+    to that replacement's API docs (plus the migration guide).
+
+    Args:
+        module (str): The removed v2 module path, e.g. ``"sagemaker.estimator"``.
+        replacement (str): Human readable v3 replacement, e.g. ``"ModelTrainer"``.
+            Optional.
+        v3_import (str): The exact v3 import statement, e.g.
+            ``"from sagemaker.train import ModelTrainer"``. Quoted verbatim so the
+            caller can copy-paste it. Optional.
+        v3_docs (str): Direct URL to the v3 replacement's API documentation, e.g.
+            the generated ``sagemaker.train.model_trainer`` page. Optional.
+
+    Raises:
+        ModuleNotFoundError: always, after emitting the deprecation warning.
+    """
+    msg = f"`{module}` was removed in the SageMaker Python SDK v3."
+    if replacement:
+        msg += f" Use {replacement}."
+    if v3_import:
+        msg += f" ({v3_import})"
+    if v3_docs:
+        msg += f"\nDocs: {v3_docs}"
+    msg += f"\nSee {V3_MIGRATION_URL} for the migration guide."
+
+    warnings.warn(msg, DeprecationWarning, stacklevel=2)
+    # The raised ModuleNotFoundError below is the loud, authoritative signal
+    # (it stops execution and carries the full message). Log at debug only, to
+    # leave a breadcrumb for log-captured environments without duplicating the
+    # message at WARNING level.
+    logger.debug(msg)
+    raise ModuleNotFoundError(msg, name=module)
+
+
+class _RemovedV2ModuleFinder(importlib.abc.MetaPathFinder):
+    """Fallback finder that gives actionable guidance for removed v2 modules.
+
+    Curated removals ship as explicit "tombstone" modules (e.g.
+    ``sagemaker/estimator.py``) that raise a precise, per-module message. This
+    finder is the *catch-all* for every other ``sagemaker.<name>`` that existed
+    in v2 but was not individually tombstoned: instead of a bare
+    ``ModuleNotFoundError: No module named 'sagemaker.foo'``, the caller gets a
+    message that says the module is not available in v3 and points to the
+    migration guide.
+
+    It is registered by appending to ``sys.meta_path``, so it only runs *after*
+    the normal import machinery has failed to locate the module. That ordering
+    guarantees it never shadows:
+      - real v3 packages (``sagemaker.core``, ``sagemaker.train``, ...), and
+      - the curated tombstone modules, which resolve as ordinary files first.
+    """
+
+    def find_spec(self, fullname, path=None, target=None):
+        """Emit guidance only for known removed v2 top-level ``sagemaker`` modules."""
+        if not fullname.startswith("sagemaker."):
+            return None
+        leaf = fullname[len("sagemaker.") :]
+        # Only guard top-level names; never touch real v3 subpackages.
+        if "." in leaf or leaf in _KNOWN_V3_TOPLEVEL:
+            return None
+        # Only guard names that were actually v2 modules. Unknown names (typos,
+        # hallucinated imports) fall through to a plain ModuleNotFoundError so we
+        # never claim something "was removed" when it never existed.
+        if leaf not in _REMOVED_V2_MODULES:
+            return None
+
+        msg = (
+            f"`{fullname}` was removed in the SageMaker Python SDK v3. "
+            "It may have moved to a new location."
+            f"\nSee {V3_MIGRATION_URL} for the migration guide."
+        )
+        warnings.warn(msg, DeprecationWarning, stacklevel=2)
+        # See raise_removed_in_v3: the raised error is the loud signal; log at
+        # debug to avoid duplicating the message at WARNING level.
+        logger.debug(msg)
+        raise ModuleNotFoundError(msg, name=fullname)
+
+
+def register_removed_module_finder():
+    """Install the fallback finder for removed v2 modules (idempotent).
+
+    Appends a single ``_RemovedV2ModuleFinder`` to ``sys.meta_path`` so it acts
+    as a last resort. Safe to call multiple times -- it installs at most one
+    instance per process.
+    """
+    if any(isinstance(f, _RemovedV2ModuleFinder) for f in sys.meta_path):
+        return
+    sys.meta_path.append(_RemovedV2ModuleFinder())
+
 
 def _warn(msg, sdk_version=None):
     """Generic warning raiser referencing V2
diff --git a/sagemaker-core/src/sagemaker/estimator.py b/sagemaker-core/src/sagemaker/estimator.py
new file mode 100644
index 0000000000..4cc11a8ed7
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/estimator.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.estimator`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.estimator",
+    replacement="`ModelTrainer`",
+    v3_import="from sagemaker.train import ModelTrainer",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.train.model_trainer.html",
+)
diff --git a/sagemaker-core/src/sagemaker/model.py b/sagemaker-core/src/sagemaker/model.py
new file mode 100644
index 0000000000..541a728937
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/model.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.model`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.model",
+    replacement="`ModelBuilder`",
+    v3_import="from sagemaker.serve import ModelBuilder",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.serve.model_builder.html",
+)
diff --git a/sagemaker-core/src/sagemaker/multidatamodel.py b/sagemaker-core/src/sagemaker/multidatamodel.py
new file mode 100644
index 0000000000..4e4e6db648
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/multidatamodel.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.multidatamodel`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.multidatamodel",
+    replacement="`ModelBuilder`",
+    v3_import="from sagemaker.serve import ModelBuilder",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.serve.model_builder.html",
+)
diff --git a/sagemaker-core/src/sagemaker/pipeline.py b/sagemaker-core/src/sagemaker/pipeline.py
new file mode 100644
index 0000000000..dbe7c6a2d7
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/pipeline.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.pipeline`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.pipeline",
+    replacement="`Pipeline`",
+    v3_import="from sagemaker.mlops.workflow.pipeline import Pipeline",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.mlops.workflow.pipeline.html",
+)
diff --git a/sagemaker-core/src/sagemaker/predictor.py b/sagemaker-core/src/sagemaker/predictor.py
new file mode 100644
index 0000000000..5509a81253
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/predictor.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.predictor`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.predictor",
+    replacement="the `Endpoint` resource",
+    v3_import="from sagemaker.core.resources import Endpoint",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/src/sagemaker/predictor_async.py b/sagemaker-core/src/sagemaker/predictor_async.py
new file mode 100644
index 0000000000..5da343837b
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/predictor_async.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.predictor_async`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.predictor_async",
+    replacement="`ModelBuilder` (async deploy)",
+    v3_import="from sagemaker.serve import ModelBuilder",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.serve.model_builder.html",
+)
diff --git a/sagemaker-core/src/sagemaker/processing.py b/sagemaker-core/src/sagemaker/processing.py
new file mode 100644
index 0000000000..638767e985
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/processing.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.processing`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.processing",
+    replacement="the `ProcessingJob` resource",
+    v3_import="from sagemaker.core.resources import ProcessingJob",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/src/sagemaker/transformer.py b/sagemaker-core/src/sagemaker/transformer.py
new file mode 100644
index 0000000000..1a40226c6e
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/transformer.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.transformer`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.transformer",
+    replacement="the `TransformJob` resource",
+    v3_import="from sagemaker.core.resources import TransformJob",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/src/sagemaker/tuner.py b/sagemaker-core/src/sagemaker/tuner.py
new file mode 100644
index 0000000000..6ebfda507a
--- /dev/null
+++ b/sagemaker-core/src/sagemaker/tuner.py
@@ -0,0 +1,27 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Removed in v3. This module stood in the v2 SageMaker Python SDK.
+
+Importing ``sagemaker.tuner`` raises an actionable ``ModuleNotFoundError`` that
+points to the v3 replacement. See the migration guide for details.
+"""
+from __future__ import absolute_import
+
+from sagemaker.core.deprecations import raise_removed_in_v3
+
+raise_removed_in_v3(
+    module="sagemaker.tuner",
+    replacement="the `HyperParameterTuningJob` resource",
+    v3_import="from sagemaker.core.resources import HyperParameterTuningJob",
+    v3_docs="https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.core.resources.html",
+)
diff --git a/sagemaker-core/tests/unit/test_removed_v2_modules.py b/sagemaker-core/tests/unit/test_removed_v2_modules.py
new file mode 100644
index 0000000000..19a389c699
--- /dev/null
+++ b/sagemaker-core/tests/unit/test_removed_v2_modules.py
@@ -0,0 +1,244 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+"""Tests that removed v2 modules raise actionable guidance in v3."""
+from __future__ import absolute_import
+
+import importlib
+import warnings
+
+import pytest
+
+from sagemaker.core.deprecations import (
+    raise_removed_in_v3,
+    register_removed_module_finder,
+    _RemovedV2ModuleFinder,
+    V3_MIGRATION_URL,
+)
+
+# Removed v2 module -> a substring expected in the guidance message. The values
+# are verified-importable v3 symbols (see the tombstone modules under
+# src/sagemaker/); the message also carries the exact import and a docs URL.
+REMOVED_MODULES = {
+    "sagemaker.estimator": "ModelTrainer",
+    "sagemaker.model": "ModelBuilder",
+    "sagemaker.predictor": "Endpoint",
+    "sagemaker.base_predictor": "Endpoint",
+    "sagemaker.predictor_async": "ModelBuilder",
+    "sagemaker.transformer": "TransformJob",
+    "sagemaker.tuner": "HyperParameterTuningJob",
+    "sagemaker.processing": "ProcessingJob",
+    "sagemaker.pipeline": "Pipeline",
+    "sagemaker.multidatamodel": "ModelBuilder",
+    "sagemaker.automl": "AutoMLJob",
+    "sagemaker.algorithm": "ModelTrainer",
+}
+
+
+def _fresh_import(module):
+    """Import a module fresh, bypassing any cached (failed) import state."""
+    import sys
+
+    sys.modules.pop(module, None)
+    return importlib.import_module(module)
+
+
+@pytest.mark.parametrize("module,expected", sorted(REMOVED_MODULES.items()))
+def test_removed_module_raises_actionable_error(module, expected):
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        with pytest.raises(ModuleNotFoundError) as exc:
+            _fresh_import(module)
+    message = str(exc.value)
+    assert module in message
+    assert "removed in the SageMaker Python SDK v3" in message
+    assert expected in message
+    # Every tombstone points at a copy-pasteable import and a docs URL.
+    assert "from sagemaker." in message
+    assert "sagemaker.readthedocs.io/en/stable/api/generated/" in message
+    assert V3_MIGRATION_URL in message
+
+
+@pytest.mark.parametrize("module", sorted(REMOVED_MODULES))
+def test_removed_module_emits_deprecation_warning(module):
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        with pytest.raises(ModuleNotFoundError):
+            _fresh_import(module)
+    assert any(issubclass(x.category, DeprecationWarning) for x in w)
+
+
+def test_helper_includes_import_and_docs_when_provided():
+    docs = "https://sagemaker.readthedocs.io/en/stable/api/generated/sagemaker.train.model_trainer.html"
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        with pytest.raises(ModuleNotFoundError) as exc:
+            raise_removed_in_v3(
+                module="sagemaker.estimator",
+                replacement="`ModelTrainer`",
+                v3_import="from sagemaker.train import ModelTrainer",
+                v3_docs=docs,
+            )
+    message = str(exc.value)
+    assert "from sagemaker.train import ModelTrainer" in message
+    assert docs in message
+    # ModuleNotFoundError carries the module name for tooling.
+    assert exc.value.name == "sagemaker.estimator"
+
+
+def test_helper_without_replacement_still_actionable():
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore")
+        with pytest.raises(ModuleNotFoundError) as exc:
+            raise_removed_in_v3(module="sagemaker.something")
+    message = str(exc.value)
+    assert "sagemaker.something" in message
+    assert V3_MIGRATION_URL in message
+
+
+# --- Fallback finder (catch-all for non-tombstoned removed modules) ---
+
+
+def test_finder_is_registered_on_meta_path():
+    import sys
+    import sagemaker.core  # noqa: F401  -- import registers the finder
+
+    assert any(isinstance(f, _RemovedV2ModuleFinder) for f in sys.meta_path)
+
+
+def test_finder_registered_on_bare_sagemaker_import():
+    import sys
+    import importlib
+
+    # The namespace package init registers the finder, so it is active even
+    # without importing sagemaker.core explicitly.
+    for name in [m for m in list(sys.modules) if m == "sagemaker" or m.startswith("sagemaker.")]:
+        pass  # (do not evict already-imported real modules; just assert state)
+    import sagemaker  # noqa: F401  -- runs the namespace __init__
+
+    importlib.import_module("sagemaker")
+    assert any(isinstance(f, _RemovedV2ModuleFinder) for f in sys.meta_path)
+
+
+def test_removed_module_guidance_on_first_import_in_fresh_process():
+    # Regression: a removed module as the VERY FIRST sagemaker import (before
+    # sagemaker.core is otherwise loaded) must still get guidance, not a bare
+    # error. Run in a fresh interpreter so import state cannot leak in, and
+    # capture the message from the exception itself (the console traceback
+    # formatter does not always write plain text to stderr).
+    import subprocess
+    import sys
+
+    code = (
+        "import sys\n"
+        "try:\n"
+        "    import sagemaker.estimator\n"
+        "except ModuleNotFoundError as e:\n"
+        "    sys.stdout.write(str(e))\n"
+    )
+    proc = subprocess.run([sys.executable, "-c", code], capture_output=True, text=True)
+    assert "was removed in the SageMaker Python SDK v3" in proc.stdout
+    assert "from sagemaker.train import ModelTrainer" in proc.stdout
+
+
+def test_register_is_idempotent():
+    import sys
+
+    register_removed_module_finder()
+    register_removed_module_finder()
+    finders = [f for f in sys.meta_path if isinstance(f, _RemovedV2ModuleFinder)]
+    assert len(finders) == 1
+
+
+def test_finder_is_appended_not_prepended():
+    # As a last resort it must sit at the end so real/tombstone modules resolve
+    # first. Being in the second half of meta_path is a sufficient proxy.
+    import sys
+
+    register_removed_module_finder()
+    idx = next(i for i, f in enumerate(sys.meta_path) if isinstance(f, _RemovedV2ModuleFinder))
+    assert idx >= len(sys.meta_path) // 2
+
+
+@pytest.mark.parametrize("module", ["sagemaker.clarify", "sagemaker.session", "sagemaker.network"])
+def test_uncovered_module_falls_back_to_guidance(module):
+    import sagemaker.core  # noqa: F401  -- ensure finder registered
+
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        with pytest.raises(ModuleNotFoundError) as exc:
+            _fresh_import(module)
+    message = str(exc.value)
+    assert module in message
+    assert "was removed in the SageMaker Python SDK v3" in message
+    assert V3_MIGRATION_URL in message
+    assert any(issubclass(x.category, DeprecationWarning) for x in w)
+
+
+@pytest.mark.parametrize("module", ["sagemaker.foobar", "sagemaker.not_a_module", "sagemaker.zzz"])
+def test_unknown_name_gets_plain_error_not_guidance(module):
+    # Names that never existed in v2 (typos, hallucinated imports) must fall
+    # through to a plain ModuleNotFoundError -- no "was removed" claim, no
+    # migration-guide link, no deprecation warning.
+    import sagemaker.core  # noqa: F401  -- ensure finder registered
+
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        with pytest.raises(ModuleNotFoundError) as exc:
+            _fresh_import(module)
+    message = str(exc.value)
+    assert "was removed" not in message
+    assert V3_MIGRATION_URL not in message
+    assert not any(issubclass(x.category, DeprecationWarning) for x in w)
+
+
+def test_finder_passes_through_unknown_names():
+    import sagemaker.core  # noqa: F401
+
+    finder = _RemovedV2ModuleFinder()
+    # Known removed v2 module -> guarded (raises); unknown -> pass through (None).
+    assert finder.find_spec("sagemaker.foobar") is None
+    assert finder.find_spec("sagemaker.definitely_not_real") is None
+
+
+@pytest.mark.parametrize(
+    "module",
+    [
+        "sagemaker.core",
+        "sagemaker.train",
+        "sagemaker.serve",
+        "sagemaker.mlops",
+        "sagemaker.lineage",
+    ],
+)
+def test_finder_does_not_shadow_real_v3_packages(module):
+    import sagemaker.core  # noqa: F401  -- ensure finder registered
+
+    # The fallback finder must not intercept real v3 packages: find_spec must
+    # return None (pass-through), regardless of whether the package happens to
+    # be installed in the current environment. (The sagemaker-core unit-test job
+    # installs core only, so sagemaker.train/serve/mlops are not importable
+    # there -- asserting find_spec pass-through avoids that false dependency.)
+    finder = _RemovedV2ModuleFinder()
+    assert finder.find_spec(module) is None
+
+
+def test_finder_ignores_non_sagemaker_and_nested():
+    import sagemaker.core  # noqa: F401
+
+    finder = _RemovedV2ModuleFinder()
+    # Not a sagemaker module -> pass through (None).
+    assert finder.find_spec("numpy") is None
+    # Nested path under a (removed) top-level -> only the top-level is guarded.
+    assert finder.find_spec("sagemaker.workflow.steps") is None
+    # Real v3 top-level -> never guarded.
+    assert finder.find_spec("sagemaker.train") is None