diff --git a/.github/workflows/unittest.yml b/.github/workflows/unittest.yml
index c9e8f5239bf1..ad85555808e1 100644
--- a/.github/workflows/unittest.yml
+++ b/.github/workflows/unittest.yml
@@ -18,6 +18,7 @@ env:
   NOX_ENVDIR: "/tmp/shared_nox_envs"
   NOX_DEFAULT_VENV_BACKEND: "uv"
   UV_VENV_SEED: "1"
+  UV_PRERELEASE: "allow"
   # Note: PARALLEL_WORKERS must remain "1" for unit tests because running pytest concurrently
   # on the same runner VM can cause socket/IPC/process deadlocks across packages.
   PARALLEL_WORKERS: "1"
@@ -29,12 +30,13 @@ jobs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
       is_full_run: ${{ steps.check-label.outputs.is_full_run }}
     env:
-      MAX_SHARDS: 16
+      MAX_SHARDS: 20
       # Define weights for long-running unit tests to balance shard execution time
       # Each weight is roughly 1 minute of expected execution time
       # Default for unset packages is 1
       PACKAGE_WEIGHTS: |
         bigframes: 6
+        sqlalchemy-spanner: 6
         google-ai-generativelanguage: 4
         google-auth: 5
         google-cloud-compute: 12
@@ -81,9 +83,8 @@ jobs:
     if: needs.initialize.outputs.matrix != '[]' && needs.initialize.outputs.matrix != ''
     runs-on: ubuntu-22.04
     strategy:
-      fail-fast: true
       matrix:
-        python: ['3.10', "3.11", "3.12", "3.13", "3.14"]
+        python: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
         package_shard: ${{ fromJson(needs.initialize.outputs.matrix) }}
     name: ${{ matrix.package_shard.is_sharded && format('unit ({0}, {1})', matrix.python, matrix.package_shard.name) || format('unit ({0})', matrix.python) }}
     steps:
@@ -100,10 +101,40 @@ jobs:
       with:
         python-version: ${{ matrix.python }}
         cache: 'pip'
-    - name: Install nox
+        allow-prereleases: true
+    - name: Setup uv
+      uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5
+      with:
+        enable-cache: true
+        cache-dependency-glob: 'packages/**/testing/constraints*.txt'
+    - name: Install nox and nox-uv
       run: |
-        python -m pip install --upgrade setuptools pip wheel
-        python -m pip install nox uv
+        uv pip install --system nox nox-uv
+    # Caches local wheels for Python 3.15+ to avoid repeatedly downloading or building heavy libraries.
+    # Follow https://github.com/grpc/grpc/issues/41010 for updates.
+    - name: Cache Built Python 3.15 Wheels
+      if: matrix.python == '3.15'
+      uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
+      with:
+        path: .uv-wheel-cache
+        key: ${{ runner.os }}-uv-wheels-3.15-${{ hashFiles('packages/**/testing/constraints*.txt') }}
+        restore-keys: |
+          ${{ runner.os }}-uv-wheels-3.15-
+    # TODO: Remove this step once official Python 3.15 wheels for grpcio are published to PyPI.
+    # See https://github.com/grpc/grpc/issues/41010#issuecomment-4848264910 for details.
+    - name: Install grpcio wheel for Python 3.15
+      if: matrix.python == '3.15'
+      run: |
+        mkdir -p .uv-wheel-cache
+        WHEEL_FILE=".uv-wheel-cache/grpcio-1.83.0.dev0-cp315-cp315-manylinux2014_x86_64.manylinux_2_17_x86_64.whl"
+        if [ ! -f "$WHEEL_FILE" ]; then
+          curl -L "https://packages.grpc.io/archive/2026/06/5ccdab32010f762634e1082d19be53cf60458456-b37e49c7-5e62-4cbe-870a-c599bb907b04/python/grpcio/grpcio-1.83.0.dev0-cp315-cp315-manylinux2014_x86_64.manylinux_2_17_x86_64.whl" -o "$WHEEL_FILE"
+        fi
+        echo "d7706633cd5d97a8b8d3c6ed36c5940722a9b5cbb47f0d10bc433ee27af36ff0  $WHEEL_FILE" | sha256sum -c
+        uv pip install --system "$WHEEL_FILE"
+        echo "UV_FIND_LINKS=${{ github.workspace }}/.uv-wheel-cache" >> $GITHUB_ENV
+        echo "UV_CACHE_DIR=${{ github.workspace }}/.uv-wheel-cache" >> $GITHUB_ENV
+        echo "UV_PRERELEASE=allow" >> $GITHUB_ENV
     - name: Run unit tests for ${{ matrix.package_shard.description }}
       env:
         BUILD_TYPE: presubmit
diff --git a/ci/get_package_shards.py b/ci/get_package_shards.py
index 77cc191cc3ac..465be8c4498e 100644
--- a/ci/get_package_shards.py
+++ b/ci/get_package_shards.py
@@ -165,7 +165,7 @@ def group_packages(packages_map):
 
     # Dynamically determine target weight to balance across max shards.
     max_shards = int(os.environ.get("MAX_SHARDS", 16))
-    target_weight = max(10, math.ceil(total_weight / max_shards))
+    target_weight = max(6, math.ceil(total_weight / max_shards))
 
     shards_list = []
     current_shard_items = []
diff --git a/ci/run_single_test.sh b/ci/run_single_test.sh
index 8f4a034d5097..646bb8db99f8 100755
--- a/ci/run_single_test.sh
+++ b/ci/run_single_test.sh
@@ -90,6 +90,11 @@ case ${TEST_TYPE} in
             nox -s unit-3.14
             retval=$?
             ;;
+        "3.15")
+            # This is needed to speed up builds
+            nox --force-venv-backend uv -s unit-3.15
+            retval=$?
+            ;;
         *)
             echo "unsupported PY_VERSION"
             exit 1
diff --git a/packages/bigframes/bigframes/_magics.py b/packages/bigframes/bigframes/_magics.py
index f536108d53d4..019910be9513 100644
--- a/packages/bigframes/bigframes/_magics.py
+++ b/packages/bigframes/bigframes/_magics.py
@@ -37,6 +37,9 @@
 )
 def _cell_magic(line, cell):
     ipython = get_ipython()
+    if ipython is None:
+        return
+
     args = magic_arguments.parse_argstring(_cell_magic, line)
     if not cell:
         print("Query is missing.")
diff --git a/packages/bigframes/noxfile.py b/packages/bigframes/noxfile.py
index 8cbbddfc61aa..839e6e0e1158 100644
--- a/packages/bigframes/noxfile.py
+++ b/packages/bigframes/noxfile.py
@@ -60,7 +60,7 @@
 
 DEFAULT_PYTHON_VERSION = "3.14"
 
-ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     PYTEST_VERSION,
@@ -283,6 +283,10 @@ def run_unit(session, install_test_extra):
 @nox.session(python=ALL_PYTHON)
 @nox.parametrize("test_extra", [True, False])
 def unit(session, test_extra):
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for pyarrow. Also pyproj wheels are needed for dependency geopandas."
+        )
     if test_extra:
         run_unit(session, install_test_extra=test_extra)
     else:
diff --git a/packages/bigquery-magics/noxfile.py b/packages/bigquery-magics/noxfile.py
index 0a2a15597580..7a273ac28419 100644
--- a/packages/bigquery-magics/noxfile.py
+++ b/packages/bigquery-magics/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
@@ -237,6 +238,10 @@ def install_unittest_dependencies(session, *constraints):
 @nox.session(python=UNIT_TEST_PYTHON_VERSIONS)
 def unit(session):
     # Install all test dependencies, then install this package in-place.
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for pyproj needed for dependency geopandas"
+        )
 
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
diff --git a/packages/bigquery-magics/testing/constraints-3.15.txt b/packages/bigquery-magics/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/db-dtypes/noxfile.py b/packages/db-dtypes/noxfile.py
index afd1ab00a637..b26f72f7a285 100644
--- a/packages/db-dtypes/noxfile.py
+++ b/packages/db-dtypes/noxfile.py
@@ -42,6 +42,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
@@ -302,6 +303,8 @@ def prerelease(session, tests_path):
 @nox.parametrize("test_type", ["unit", "compliance"])
 def unit(session, test_type):
     """Run the unit test suite."""
+    if session.python == "3.15":
+        session.skip("Skipping 3.15 until wheels are available for pyarrow.")
 
     # Compliance tests only run on the latest Python version
     if test_type == "compliance" and session.python != DEFAULT_PYTHON_VERSION:
diff --git a/packages/db-dtypes/testing/constraints-3.15.txt b/packages/db-dtypes/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/django-google-spanner/noxfile.py b/packages/django-google-spanner/noxfile.py
index b867418df7bf..612fafe793f9 100644
--- a/packages/django-google-spanner/noxfile.py
+++ b/packages/django-google-spanner/noxfile.py
@@ -34,6 +34,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 ALL_PYTHON = list(UNIT_TEST_PYTHON_VERSIONS)
 
diff --git a/packages/django-google-spanner/testing/constraints-3.15.txt b/packages/django-google-spanner/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/gcp-sphinx-docfx-yaml/noxfile.py b/packages/gcp-sphinx-docfx-yaml/noxfile.py
index 4fb1a1e9baa1..eba996702d4d 100644
--- a/packages/gcp-sphinx-docfx-yaml/noxfile.py
+++ b/packages/gcp-sphinx-docfx-yaml/noxfile.py
@@ -18,7 +18,7 @@
 import nox
 
 DEFAULT_PYTHON_VERSION = "3.14"
-UNIT_TEST_PYTHON_VERSIONS = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+UNIT_TEST_PYTHON_VERSIONS = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 # Path to the centralized mypy configuration file at the repository root.
 # Search upwards to support running nox from both monorepo packages and integration test goldens.
@@ -166,7 +166,7 @@ def unit(session):
     # Re-enable 3.11, 3.12, and 3.13 after environment verification.
     # TODO(https://github.com/googleapis/google-cloud-python/issues/16176):
     # Track 3.14 compatibility as upstream dependencies stabilize.
-    _skip_python_session(session, ["3.11", "3.12", "3.13", "3.14"])
+    _skip_python_session(session, ["3.11", "3.12", "3.13", "3.14", "3.15"])
     session.install("-r", "requirements.txt")
     session.install("pytest", "pytest-cov")
     session.run(
diff --git a/packages/google-api-core/noxfile.py b/packages/google-api-core/noxfile.py
index fca53607bdb2..673b91043bd6 100644
--- a/packages/google-api-core/noxfile.py
+++ b/packages/google-api-core/noxfile.py
@@ -31,8 +31,7 @@
 RUFF_VERSION = "ruff==0.14.14"
 LINT_PATHS = ["docs", "google", "tests", "noxfile.py", "setup.py"]
 
-ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14"]
-SUPPORTED_PYTHON_VERSIONS = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 
 DEFAULT_PYTHON_VERSION = "3.14"
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
@@ -231,14 +230,14 @@ def default(
     if prerelease:
         install_prerelease_dependencies(
             session,
-            f"{constraints_dir}/constraints-{constraints_type}{SUPPORTED_PYTHON_VERSIONS[0]}.txt",
+            f"{constraints_dir}/constraints-{constraints_type}{ALL_PYTHON[0]}.txt",
         )
         # This *must* be the last install command to get the package from source.
         session.install("-e", lib_with_extras, "--no-deps")
     elif install_deps_from_source:
         install_core_deps_dependencies(
             session,
-            f"{constraints_dir}/constraints-{constraints_type}{SUPPORTED_PYTHON_VERSIONS[0]}.txt",
+            f"{constraints_dir}/constraints-{constraints_type}{ALL_PYTHON[0]}.txt",
         )
         # This *must* be the last install command to get the package from source.
         session.install("-e", lib_with_extras, "--no-deps")
diff --git a/packages/google-api-core/testing/constraints-3.15.txt b/packages/google-api-core/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-auth-httplib2/noxfile.py b/packages/google-auth-httplib2/noxfile.py
index 162301d4f13b..df530819a42d 100644
--- a/packages/google-auth-httplib2/noxfile.py
+++ b/packages/google-auth-httplib2/noxfile.py
@@ -39,6 +39,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-auth-httplib2/testing/constraints-3.15.txt b/packages/google-auth-httplib2/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-auth-oauthlib/noxfile.py b/packages/google-auth-oauthlib/noxfile.py
index 1a7f043e7461..eb5419d94ec2 100644
--- a/packages/google-auth-oauthlib/noxfile.py
+++ b/packages/google-auth-oauthlib/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-auth-oauthlib/testing/constraints-3.15.txt b/packages/google-auth-oauthlib/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-auth/noxfile.py b/packages/google-auth/noxfile.py
index 38e5f4d82f70..86a31f3b4660 100644
--- a/packages/google-auth/noxfile.py
+++ b/packages/google-auth/noxfile.py
@@ -46,10 +46,7 @@
 
 DEFAULT_PYTHON_VERSION = "3.14"
 
-# TODO(https://github.com/googleapis/gapic-generator-python/issues/2450):
-# Switch this to Python 3.15 alpha1
-# https://peps.python.org/pep-0790/
-PREVIEW_PYTHON_VERSION = "3.14"
+PREVIEW_PYTHON_VERSION = "3.15"
 
 UNIT_TEST_PYTHON_VERSIONS = [
     "3.10",
@@ -57,6 +54,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 ALL_PYTHON = UNIT_TEST_PYTHON_VERSIONS.copy()
 
diff --git a/packages/google-auth/testing/constraints-3.15.txt b/packages/google-auth/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-access-context-manager/noxfile.py b/packages/google-cloud-access-context-manager/noxfile.py
index ab17625e3f2e..dfe8d9a71759 100644
--- a/packages/google-cloud-access-context-manager/noxfile.py
+++ b/packages/google-cloud-access-context-manager/noxfile.py
@@ -37,9 +37,10 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
-DEFAULT_PYTHON_VERSION = UNIT_TEST_PYTHON_VERSIONS[-1]
+DEFAULT_PYTHON_VERSION = "3.14"
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-cloud-access-context-manager/testing/constraints-3.15.txt b/packages/google-cloud-access-context-manager/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-audit-log/noxfile.py b/packages/google-cloud-audit-log/noxfile.py
index f35f358125a4..55c291dcf63e 100644
--- a/packages/google-cloud-audit-log/noxfile.py
+++ b/packages/google-cloud-audit-log/noxfile.py
@@ -37,9 +37,10 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
-DEFAULT_PYTHON_VERSION = UNIT_TEST_PYTHON_VERSIONS[-1]
+DEFAULT_PYTHON_VERSION = "3.14"
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-cloud-audit-log/testing/constraints-3.15.txt b/packages/google-cloud-audit-log/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-bigquery/.coveragerc b/packages/google-cloud-bigquery/.coveragerc
index e78e7a931e09..a22bacb57e19 100644
--- a/packages/google-cloud-bigquery/.coveragerc
+++ b/packages/google-cloud-bigquery/.coveragerc
@@ -2,7 +2,7 @@
 branch = True
 
 [report]
-fail_under = 100
+fail_under = 99
 show_missing = True
 omit =
     google/cloud/bigquery/__init__.py
diff --git a/packages/google-cloud-bigquery/noxfile.py b/packages/google-cloud-bigquery/noxfile.py
index d4accfea91a4..f4e899fc553c 100644
--- a/packages/google-cloud-bigquery/noxfile.py
+++ b/packages/google-cloud-bigquery/noxfile.py
@@ -38,7 +38,7 @@
 )
 
 DEFAULT_PYTHON_VERSION = "3.14"
-ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 UNIT_TEST_PYTHON_VERSIONS = ALL_PYTHON
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 # Path to the centralized mypy configuration file at the repository root.
@@ -180,6 +180,10 @@ def default(session, install_extras=True):
 @_calculate_duration
 def unit(session, test_type):
     """Run the unit test suite."""
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for pyarrow. Also pyproj wheels are needed for dependency geopandas."
+        )
 
     install_extras = True
     if test_type == "unit_noextras":
diff --git a/packages/google-cloud-bigquery/testing/constraints-3.15.txt b/packages/google-cloud-bigquery/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-core/noxfile.py b/packages/google-cloud-core/noxfile.py
index a86e71252c69..772c0c136b3d 100644
--- a/packages/google-cloud-core/noxfile.py
+++ b/packages/google-cloud-core/noxfile.py
@@ -32,6 +32,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 # Path to the centralized mypy configuration file at the repository root.
diff --git a/packages/google-cloud-core/testing/constraints-3.15.txt b/packages/google-cloud-core/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-dns/noxfile.py b/packages/google-cloud-dns/noxfile.py
index 55c042e6b68f..c7e04c73bc5a 100644
--- a/packages/google-cloud-dns/noxfile.py
+++ b/packages/google-cloud-dns/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-cloud-dns/testing/constraints-3.15.txt b/packages/google-cloud-dns/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-documentai-toolbox/noxfile.py b/packages/google-cloud-documentai-toolbox/noxfile.py
index d046a6f3d39b..18a537cb9bda 100644
--- a/packages/google-cloud-documentai-toolbox/noxfile.py
+++ b/packages/google-cloud-documentai-toolbox/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
@@ -199,6 +200,10 @@ def install_unittest_dependencies(session, *constraints):
 )
 def unit(session, protobuf_implementation):
     # Install all test dependencies, then install this package in-place.
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for 1. numba (from dependency pandas[performance]) 2. lxml (from dependency pikepdf) 3. pyarrow."
+        )
 
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
diff --git a/packages/google-cloud-documentai-toolbox/setup.py b/packages/google-cloud-documentai-toolbox/setup.py
index 0d71958686e5..8765caa5b94a 100644
--- a/packages/google-cloud-documentai-toolbox/setup.py
+++ b/packages/google-cloud-documentai-toolbox/setup.py
@@ -54,7 +54,10 @@
     },
     install_requires=(
         "google-api-core>=2.25.0, <3.0.0",
-        "pandas[performance,gcp]>=2.0.0, <3.0.0",
+        # For Python < 3.15: Install with performance extras (which includes numba)
+        "pandas[performance,gcp]>=2.0.0, <3.0.0; python_version < '3.15'",
+        # pandas[performance] requires numba which does not have 3.15 support yet
+        "pandas[gcp]>=2.0.0, <3.0.0;python_version>='3.15'",
         "pyarrow>=15.0.0, <23.0.0",
         "tabulate>=0.9.0, <1.0.0",
         "proto-plus>=1.26.1, <2.0.0",
diff --git a/packages/google-cloud-documentai-toolbox/testing/constraints-3.15.txt b/packages/google-cloud-documentai-toolbox/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..af6f7f358d70
--- /dev/null
+++ b/packages/google-cloud-documentai-toolbox/testing/constraints-3.15.txt
@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+# This constraints file is required for unit tests.
+# List all library dependencies and extras in this file.
+google-api-core
+pandas
+proto-plus
+grpc-google-iam-v1
+google-cloud-bigquery
+google-cloud-documentai
+google-cloud-storage
+numpy
+pikepdf
+numba>=0.63.0b1
diff --git a/packages/google-cloud-ndb/noxfile.py b/packages/google-cloud-ndb/noxfile.py
index 93564ffa28e0..cb957a674ed1 100644
--- a/packages/google-cloud-ndb/noxfile.py
+++ b/packages/google-cloud-ndb/noxfile.py
@@ -29,7 +29,7 @@
 LOCAL_DEPS = ("google-api-core", "google-cloud-core")
 NOX_DIR = os.path.abspath(os.path.dirname(__file__))
 DEFAULT_INTERPRETER = "3.14"
-ALL_INTERPRETERS = ("3.10", "3.11", "3.12", "3.13", "3.14")
+ALL_INTERPRETERS = ("3.10", "3.11", "3.12", "3.13", "3.14", "3.15")
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 # Path to the centralized mypy configuration file at the repository root.
 # Search upwards to support running nox from both monorepo packages and integration test goldens.
diff --git a/packages/google-cloud-ndb/testing/constraints-3.15.txt b/packages/google-cloud-ndb/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..0d0adf684566
--- /dev/null
+++ b/packages/google-cloud-ndb/testing/constraints-3.15.txt
@@ -0,0 +1,8 @@
+# We use the constraints file for the latest Python version
+# (currently this file) to check that the latest
+# major versions of dependencies are supported in setup.py.
+# List all library dependencies and extras in this file.
+# Require the latest major version be installed for each dependency.
+# e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0",
+# Then this file should have google-cloud-foo>=1
+redis>=7
diff --git a/packages/google-cloud-runtimeconfig/noxfile.py b/packages/google-cloud-runtimeconfig/noxfile.py
index f4e52787ebf7..75f3c0a98e3f 100644
--- a/packages/google-cloud-runtimeconfig/noxfile.py
+++ b/packages/google-cloud-runtimeconfig/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/google-cloud-runtimeconfig/testing/constraints-3.15.txt b/packages/google-cloud-runtimeconfig/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-cloud-spanner-dbapi-driver/noxfile.py b/packages/google-cloud-spanner-dbapi-driver/noxfile.py
index 39b30c73916b..b03d6ac78d4d 100644
--- a/packages/google-cloud-spanner-dbapi-driver/noxfile.py
+++ b/packages/google-cloud-spanner-dbapi-driver/noxfile.py
@@ -38,15 +38,13 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 DEFAULT_PYTHON_VERSION = "3.14"
 DOCS_PYTHON_VERSION = "3.10"
 
-# TODO(https://github.com/googleapis/gapic-generator-python/issues/2450):
-# Switch this to Python 3.15 alpha1
-# https://peps.python.org/pep-0790/
-PREVIEW_PYTHON_VERSION = "3.14"
+PREVIEW_PYTHON_VERSION = "3.15"
 
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()
 # Path to the centralized mypy configuration file at the repository root.
diff --git a/packages/google-cloud-spanner-dbapi-driver/testing/constraints-3.15.txt b/packages/google-cloud-spanner-dbapi-driver/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..2d4c01d5696a
--- /dev/null
+++ b/packages/google-cloud-spanner-dbapi-driver/testing/constraints-3.15.txt
@@ -0,0 +1,4 @@
+# -*- coding: utf-8 -*-
+# This constraints file is required for unit tests.
+# List all library dependencies and extras in this file.
+spannerlib-python
diff --git a/packages/google-cloud-storage/noxfile.py b/packages/google-cloud-storage/noxfile.py
index 8e206c4cca76..7f8f561031fd 100644
--- a/packages/google-cloud-storage/noxfile.py
+++ b/packages/google-cloud-storage/noxfile.py
@@ -279,6 +279,10 @@ def install_unittest_dependencies(session, *constraints):
 def unit(session, protobuf_implementation):
     # Install all test dependencies, then install this package in-place.
 
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until compatible wheels are available for google-crc32c"
+        )
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
diff --git a/packages/google-cloud-testutils/noxfile.py b/packages/google-cloud-testutils/noxfile.py
index caebbf8ef459..c7bde14d4e51 100644
--- a/packages/google-cloud-testutils/noxfile.py
+++ b/packages/google-cloud-testutils/noxfile.py
@@ -33,7 +33,7 @@
 # Error if a python version is missing
 nox.options.error_on_missing_interpreters = True
 
-ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 DEFAULT_PYTHON_VERSION = "3.14"
 BLACK_VERSION = "black==23.7.0"
 RUFF_VERSION = "ruff==0.14.14"
diff --git a/packages/google-cloud-testutils/testing/constraints-3.15.txt b/packages/google-cloud-testutils/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/google-resumable-media/noxfile.py b/packages/google-resumable-media/noxfile.py
index 6d0f35f30375..3dc0eb922231 100644
--- a/packages/google-resumable-media/noxfile.py
+++ b/packages/google-resumable-media/noxfile.py
@@ -37,7 +37,7 @@
 RUFF_VERSION = "ruff==0.14.14"
 
 DEFAULT_PYTHON_VERSION = "3.14"
-UNIT_TEST_PYTHON_VERSIONS = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+UNIT_TEST_PYTHON_VERSIONS = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 SYSTEM_TEST_PYTHON_VERSIONS = UNIT_TEST_PYTHON_VERSIONS
 
 # Error if a python version is missing
diff --git a/packages/google-resumable-media/testing/constraints-3.15.txt b/packages/google-resumable-media/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/googleapis-common-protos/noxfile.py b/packages/googleapis-common-protos/noxfile.py
index e43d6651c824..78fd0cbf4ff9 100644
--- a/packages/googleapis-common-protos/noxfile.py
+++ b/packages/googleapis-common-protos/noxfile.py
@@ -37,9 +37,10 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
-DEFAULT_PYTHON_VERSION = UNIT_TEST_PYTHON_VERSIONS[-1]
+DEFAULT_PYTHON_VERSION = "3.14"
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/googleapis-common-protos/testing/constraints-3.15.txt b/packages/googleapis-common-protos/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/grpc-google-iam-v1/noxfile.py b/packages/grpc-google-iam-v1/noxfile.py
index 291eb1341764..7b66e0144f73 100644
--- a/packages/grpc-google-iam-v1/noxfile.py
+++ b/packages/grpc-google-iam-v1/noxfile.py
@@ -37,9 +37,10 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
-DEFAULT_PYTHON_VERSION = UNIT_TEST_PYTHON_VERSIONS[-1]
+DEFAULT_PYTHON_VERSION = "3.14"
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
diff --git a/packages/grpc-google-iam-v1/testing/constraints-3.15.txt b/packages/grpc-google-iam-v1/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/pandas-gbq/noxfile.py b/packages/pandas-gbq/noxfile.py
index aabc6426becb..0021226416cd 100644
--- a/packages/pandas-gbq/noxfile.py
+++ b/packages/pandas-gbq/noxfile.py
@@ -41,6 +41,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 UNIT_TEST_STANDARD_DEPENDENCIES = [
@@ -253,6 +254,11 @@ def default(session):
 @_calculate_duration
 def unit(session):
     """Run the unit test suite."""
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for pyarrow. Also pyproj wheels are needed for dependency geopandas."
+        )
+
     default(session)
 
 
diff --git a/packages/pandas-gbq/testing/constraints-3.15.txt b/packages/pandas-gbq/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/proto-plus/noxfile.py b/packages/proto-plus/noxfile.py
index 57a12b5eaa13..5f56955863c8 100644
--- a/packages/proto-plus/noxfile.py
+++ b/packages/proto-plus/noxfile.py
@@ -47,6 +47,7 @@
     "3.12",
     "3.13",
     "3.14",
+    "3.15",
 ]
 
 # Error if a python version is missing
diff --git a/packages/proto-plus/testing/constraints-3.15.txt b/packages/proto-plus/testing/constraints-3.15.txt
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/sqlalchemy-spanner/tests/mockserver_tests/test_tags.py b/packages/sqlalchemy-spanner/tests/mockserver_tests/test_tags.py
index 403203ed9e47..da538d5f0c64 100644
--- a/packages/sqlalchemy-spanner/tests/mockserver_tests/test_tags.py
+++ b/packages/sqlalchemy-spanner/tests/mockserver_tests/test_tags.py
@@ -63,7 +63,7 @@ def test_transaction_tag(self):
 
         add_singer_query_result("SELECT singers.id, singers.name\n" + "FROM singers")
         add_single_singer_query_result(
-            "SELECT singers.id AS singers_id, singers.name AS singers_name\n"
+            "SELECT singers.id, singers.name\n"
             "FROM singers\n"
             "WHERE singers.id = @a0"
         )