diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 19329cb21b8..2a45c776e09 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -69,7 +69,7 @@ repos:
           - attrs>=19.2.0
           - packaging
           - tomli
-          - types-pkg_resources
+          - types-setuptools
             # for mypy running on python>=3.11 since exceptiongroup is only a dependency
             # on <3.11
           - exceptiongroup>=1.0.0rc8
@@ -77,7 +77,7 @@ repos:
     hooks:
     -   id: rst
         name: rst
-        entry: rst-lint --encoding utf-8
+        entry: rst-lint
         files: ^(RELEASING.rst|README.rst|TIDELIFT.rst)$
         language: python
         additional_dependencies: [pygments, restructuredtext_lint]
diff --git a/AUTHORS b/AUTHORS
index ca2872f32a4..c5c774dcf85 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -60,6 +60,7 @@ Bruno Oliveira
 Cal Leeming
 Carl Friedrich Bolz
 Carlos Jenkins
+Casey Brooks
 Ceridwen
 Charles Cloud
 Charles Machalow
diff --git a/changelog/0007.bugfix.rst b/changelog/0007.bugfix.rst
new file mode 100644
index 00000000000..b3270c2e407
--- /dev/null
+++ b/changelog/0007.bugfix.rst
@@ -0,0 +1 @@
+Class-level marks now merge across multiple inheritance following MRO; identical duplicates are removed.
diff --git a/src/_pytest/mark/structures.py b/src/_pytest/mark/structures.py
index 800a25c9243..0e27e0823aa 100644
--- a/src/_pytest/mark/structures.py
+++ b/src/_pytest/mark/structures.py
@@ -4,6 +4,7 @@
 from typing import Any
 from typing import Callable
 from typing import Collection
+from typing import Dict
 from typing import Iterable
 from typing import Iterator
 from typing import List
@@ -363,6 +364,86 @@ def get_unpacked_marks(obj: object) -> Iterable[Mark]:
     return normalize_mark_list(mark_list)
 
 
+def get_unpacked_class_marks(cls: type) -> List[Mark]:
+    """Return all unique marks declared on a class following its MRO."""
+
+    def _mark_components(
+        mark: Mark,
+    ) -> Tuple[str, Tuple[Any, ...], Tuple[Tuple[str, Any], ...]]:
+        return (
+            mark.name,
+            tuple(_freeze(arg) for arg in mark.args),
+            tuple(
+                sorted((name, _freeze(value)) for name, value in mark.kwargs.items())
+            ),
+        )
+
+    def _freeze(value: Any) -> Any:
+        if isinstance(value, MarkDecorator):
+            return ("MarkDecorator", *_mark_components(value.mark))
+        if isinstance(value, Mark):
+            return ("Mark", *_mark_components(value))
+        if isinstance(value, (list, tuple)):
+            return tuple(_freeze(v) for v in value)
+        if isinstance(value, set):
+            return tuple(sorted(_freeze(v) for v in value))
+        if isinstance(value, dict):
+            return tuple(sorted((k, _freeze(v)) for k, v in value.items()))
+        return value
+
+    def _mark_key(
+        mark: Mark,
+    ) -> Tuple[str, Tuple[Any, ...], Tuple[Tuple[str, Any], ...]]:
+        return _mark_components(mark)
+
+    def _marks_for(klass: type, cache: Dict[type, List[Mark]]) -> List[Mark]:
+        cached = cache.get(klass)
+        if cached is not None:
+            return cached
+        raw = klass.__dict__.get("pytestmark", [])
+        if not isinstance(raw, list):
+            raw = [raw]
+        marks = list(normalize_mark_list(raw))
+        cache[klass] = marks
+        return marks
+
+    dedup_key: Set[Tuple[str, Tuple[Any, ...], Tuple[Tuple[str, Any], ...]]] = set()
+    collected: List[Mark] = []
+    marks_cache: Dict[type, List[Mark]] = {}
+
+    for base in cls.__mro__:
+        if base is object:
+            break
+
+        marks = list(_marks_for(base, marks_cache))
+        if marks:
+            inherited_keys = {
+                _mark_key(mark)
+                for ancestor in base.__mro__[1:]
+                if ancestor is not object
+                for mark in _marks_for(ancestor, marks_cache)
+            }
+            if inherited_keys:
+                trimmed: List[Mark] = []
+                prefix_skipping = True
+                for mark in marks:
+                    key = _mark_key(mark)
+                    if prefix_skipping and key in inherited_keys:
+                        continue
+                    prefix_skipping = False
+                    trimmed.append(mark)
+                marks = trimmed
+
+        for mark in marks:
+            key = _mark_key(mark)
+            if key in dedup_key:
+                continue
+            dedup_key.add(key)
+            collected.append(mark)
+
+    return collected
+
+
 def normalize_mark_list(
     mark_list: Iterable[Union[Mark, MarkDecorator]]
 ) -> Iterable[Mark]:
diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index 3db8775061b..67ead592148 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -63,6 +63,7 @@
 from _pytest.main import Session
 from _pytest.mark import MARK_GEN
 from _pytest.mark import ParameterSet
+from _pytest.mark.structures import get_unpacked_class_marks
 from _pytest.mark.structures import get_unpacked_marks
 from _pytest.mark.structures import Mark
 from _pytest.mark.structures import MarkDecorator
@@ -311,7 +312,10 @@ def obj(self):
             # XXX evil hack
             # used to avoid Function marker duplication
             if self._ALLOW_MARKERS:
-                self.own_markers.extend(get_unpacked_marks(self.obj))
+                if isinstance(self, Class):
+                    self.own_markers.extend(get_unpacked_class_marks(obj))
+                else:
+                    self.own_markers.extend(get_unpacked_marks(obj))
                 # This assumes that `obj` is called before there is a chance
                 # to add custom keys to `self.keywords`, so no fear of overriding.
                 self.keywords.update((mark.name, mark) for mark in self.own_markers)
diff --git a/testing/test_markers_mro.py b/testing/test_markers_mro.py
new file mode 100644
index 00000000000..b2036976903
--- /dev/null
+++ b/testing/test_markers_mro.py
@@ -0,0 +1,225 @@
+import pytest
+
+
+def _register_marks(pytester: pytest.Pytester) -> None:
+    pytester.makeini(
+        """
+        [pytest]
+        markers =
+            alpha(value): mark used for MRO ordering checks
+            beta(value): class-level mark defined on subclasses
+            gamma(value): function-level mark used for ordering assertions
+            shared(value): mark used to exercise deduplication
+            method(value): additional function-level mark
+            diamond(value): mark applied in diamond inheritance scenarios
+        """
+    )
+
+
+def test_multiple_inheritance_merges_marks(pytester: pytest.Pytester) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        class BaseA:
+            pytestmark = pytest.mark.alpha("base-a")
+
+        class BaseB:
+            pytestmark = [pytest.mark.alpha("base-b")]
+
+        @pytest.mark.beta("derived")
+        class TestDerived(BaseA, BaseB):
+            @pytest.mark.gamma("method")
+            def test_method(self, request):
+                seen = [(mark.name, mark.args) for mark in request.node.iter_markers()]
+                assert seen == [
+                    ("gamma", ("method",)),
+                    ("beta", ("derived",)),
+                    ("alpha", ("base-a",)),
+                    ("alpha", ("base-b",)),
+                ]
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_function_marks_precede_class_marks(pytester: pytest.Pytester) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.alpha("base")
+        class Base:
+            pass
+
+        class TestDerived(Base):
+            pytestmark = [pytest.mark.beta("derived-list")]
+
+            @pytest.mark.method("first")
+            @pytest.mark.gamma("second")
+            def test_method(self, request):
+                names = [mark.name for mark in request.node.iter_markers()]
+                assert names[:2] == ["gamma", "method"]
+                assert names[2:] == ["beta", "alpha"]
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_diamond_inheritance_deduplicates_marks(pytester: pytest.Pytester) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.shared("root")
+        class Root:
+            pass
+
+        @pytest.mark.shared("branch")
+        @pytest.mark.alpha("left")
+        class Left(Root):
+            pass
+
+        @pytest.mark.shared("branch")
+        @pytest.mark.alpha("right")
+        class Right(Root):
+            pass
+
+        class TestLeaf(Left, Right):
+            @pytest.mark.gamma("method")
+            def test_leaf(self, request):
+                seen = [(mark.name, mark.args) for mark in request.node.iter_markers()]
+                assert seen == [
+                    ("gamma", ("method",)),
+                    ("alpha", ("left",)),
+                    ("shared", ("branch",)),
+                    ("alpha", ("right",)),
+                    ("shared", ("root",)),
+                ]
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_identical_marks_across_bases_deduped_once(
+    pytester: pytest.Pytester,
+) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        class BaseA:
+            pytestmark = [pytest.mark.shared("duplicate")]
+
+        class BaseB:
+            pytestmark = pytest.mark.shared("duplicate")
+
+        class TestDerived(BaseA, BaseB):
+            def test_marks(self, request):
+                seen = [mark.args for mark in request.node.iter_markers(name="shared")]
+                assert seen == [("duplicate",)]
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)
+
+
+def test_parametrize_marks_merge_and_dedupe(pytester: pytest.Pytester) -> None:
+    pytester.makepyfile(
+        """
+        import pytest
+
+        class ParamBaseA:
+            pytestmark = pytest.mark.parametrize("left", ["L1", "L2"])
+
+        class ParamBaseB:
+            pytestmark = [
+                pytest.mark.parametrize("right", ["R1", "R2"]),
+                pytest.mark.parametrize("left", ["L1", "L2"]),
+            ]
+
+        class TestParam(ParamBaseA, ParamBaseB):
+            def test_params(self, left, right):
+                pass
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=4)
+
+
+def test_parametrize_marks_with_param_objects(pytester: pytest.Pytester) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        class ParamBaseA:
+            pytestmark = pytest.mark.parametrize(
+                "left",
+                [
+                    pytest.param("L1", marks=pytest.mark.shared("dup")),
+                    pytest.param("L2", marks=pytest.mark.alpha("left")),
+                ],
+            )
+
+        class ParamBaseB:
+            pytestmark = [
+                pytest.mark.parametrize(
+                    "right",
+                    [
+                        pytest.param("R1", marks=pytest.mark.shared("dup")),
+                        pytest.param("R2", marks=pytest.mark.beta("right")),
+                    ],
+                )
+            ]
+
+        class TestParamCombined(ParamBaseA, ParamBaseB):
+            def test_params(self, left, right, request):
+                shared_args = {mark.args for mark in request.node.iter_markers(name="shared")}
+                if left == "L1" or right == "R1":
+                    assert shared_args == {("dup",)}
+                else:
+                    assert shared_args == set()
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=4)
+
+
+def test_class_pytestmark_forms_supported(pytester: pytest.Pytester) -> None:
+    _register_marks(pytester)
+    pytester.makepyfile(
+        """
+        import pytest
+
+        class Decorated:
+            pytestmark = [pytest.mark.alpha("decorated")]
+
+        @pytest.mark.beta("derived")
+        class TestDerived(Decorated):
+            @pytest.mark.gamma("method")
+            def test_forms(self, request):
+                seen = [(mark.name, mark.args) for mark in request.node.iter_markers()]
+                assert seen == [
+                    ("gamma", ("method",)),
+                    ("beta", ("derived",)),
+                    ("alpha", ("decorated",)),
+                ]
+        """
+    )
+
+    result = pytester.runpytest()
+    result.assert_outcomes(passed=1)