diff --git a/setuptools/config/_apply_pyprojecttoml.py b/setuptools/config/_apply_pyprojecttoml.py
index 08a10bcdcc..83214e238b 100644
--- a/setuptools/config/_apply_pyprojecttoml.py
+++ b/setuptools/config/_apply_pyprojecttoml.py
@@ -57,6 +57,7 @@ def apply(dist: Distribution, config: dict, filename: StrPath) -> Distribution:
     os.chdir(root_dir)
     try:
         dist._finalize_requires()
+        dist._finalize_license_expression()
         dist._finalize_license_files()
     finally:
         os.chdir(current_directory)
diff --git a/setuptools/dist.py b/setuptools/dist.py
index 151f9a851f..51a0ddd52c 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -12,6 +12,7 @@
 from typing import TYPE_CHECKING, Any, Union
 
 from more_itertools import partition, unique_everseen
+from packaging.licenses import canonicalize_license_expression
 from packaging.markers import InvalidMarker, Marker
 from packaging.specifiers import InvalidSpecifier, SpecifierSet
 from packaging.version import Version
@@ -26,6 +27,7 @@
 from ._reqs import _StrOrIter
 from .config import pyprojecttoml, setupcfg
 from .discovery import ConfigDiscovery
+from .errors import InvalidConfigError
 from .monkey import get_unpatched
 from .warnings import InformationOnly, SetuptoolsDeprecationWarning
 
@@ -398,6 +400,23 @@ def _normalize_requires(self):
             k: list(map(str, _reqs.parse(v or []))) for k, v in extras_require.items()
         }
 
+    def _finalize_license_expression(self) -> None:
+        """Normalize license and license_expression."""
+        license_expr = self.metadata.license_expression
+        if license_expr:
+            normalized = canonicalize_license_expression(license_expr)
+            if license_expr != normalized:
+                InformationOnly.emit(f"Normalizing '{license_expr}' to '{normalized}'")
+                self.metadata.license_expression = normalized
+
+            for cl in self.metadata.get_classifiers():
+                if not cl.startswith("License :: "):
+                    continue
+                raise InvalidConfigError(
+                    "License classifier are deprecated in favor of the license expression. "
+                    f"Remove the '{cl}' classifier."
+                )
+
     def _finalize_license_files(self) -> None:
         """Compute names of all license files which should be included."""
         license_files: list[str] | None = self.metadata.license_files
@@ -649,6 +668,7 @@ def parse_config_files(
             pyprojecttoml.apply_configuration(self, filename, ignore_option_errors)
 
         self._finalize_requires()
+        self._finalize_license_expression()
         self._finalize_license_files()
 
     def fetch_build_eggs(
diff --git a/setuptools/tests/config/test_apply_pyprojecttoml.py b/setuptools/tests/config/test_apply_pyprojecttoml.py
index b44c479998..c90f7aadc2 100644
--- a/setuptools/tests/config/test_apply_pyprojecttoml.py
+++ b/setuptools/tests/config/test_apply_pyprojecttoml.py
@@ -22,7 +22,7 @@
 from setuptools.config import expand, pyprojecttoml, setupcfg
 from setuptools.config._apply_pyprojecttoml import _MissingDynamic, _some_attrgetter
 from setuptools.dist import Distribution
-from setuptools.errors import RemovedConfigError
+from setuptools.errors import InvalidConfigError, RemovedConfigError
 
 from .downloads import retrieve_file, urls_from_file
 
@@ -174,7 +174,10 @@ def main_tomatoes(): pass
   {email = "hi@pradyunsg.me"},
   {name = "Tzu-Ping Chung"}
 ]
-license = "MIT"
+license = "mit or apache-2.0"  # should be normalized in metadata
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+]
 """
 
 
@@ -285,8 +288,8 @@ def test_utf8_maintainer_in_metadata(  # issue-3663
         pytest.param(
             PEP639_LICENSE_EXPRESSION,
             None,
-            'MIT',
-            'License-Expression: MIT',
+            'MIT OR Apache-2.0',
+            'License-Expression: MIT OR Apache-2.0',
             id='license-expression',
         ),
     ),
@@ -313,6 +316,18 @@ def test_license_in_metadata(
     assert content_str in content
 
 
+def test_license_expression_with_bad_classifier(tmp_path):
+    text = PEP639_LICENSE_EXPRESSION.rsplit("\n", 2)[0]
+    pyproject = _pep621_example_project(
+        tmp_path,
+        "README",
+        f"{text}\n    \"License :: OSI Approved :: MIT License\"\n]",
+    )
+    msg = "License classifier are deprecated.*'License :: OSI Approved :: MIT License'"
+    with pytest.raises(InvalidConfigError, match=msg):
+        pyprojecttoml.apply_configuration(makedist(tmp_path), pyproject)
+
+
 class TestLicenseFiles:
     def base_pyproject(self, tmp_path, additional_text):
         pyproject = _pep621_example_project(tmp_path, "README")