diff --git a/changelog.d/1189.added.rst b/changelog.d/1189.added.rst
new file mode 100644
index 00000000..889feecf
--- /dev/null
+++ b/changelog.d/1189.added.rst
@@ -0,0 +1 @@
+Raise a ``pytest.UsageError`` on invalid ``asyncio_default_fixture_loop_scope`` and ``asyncio_default_test_loop_scope`` configuration values. (`#1189 <https://github.com/pytest-dev/pytest-asyncio/pull/1189>`_)
diff --git a/pytest_asyncio/plugin.py b/pytest_asyncio/plugin.py
index ec52ee4c..8eb99c9d 100644
--- a/pytest_asyncio/plugin.py
+++ b/pytest_asyncio/plugin.py
@@ -229,10 +229,25 @@ def _get_asyncio_debug(config: Config) -> bool:
 """
 
 
+def _validate_scope(scope: str | None, option_name: str) -> None:
+    if scope is None:
+        return
+    valid_scopes = [s.value for s in Scope]
+    if scope not in valid_scopes:
+        raise pytest.UsageError(
+            f"{scope!r} is not a valid {option_name}. "
+            f"Valid scopes are: {', '.join(valid_scopes)}."
+        )
+
+
 def pytest_configure(config: Config) -> None:
-    default_loop_scope = config.getini("asyncio_default_fixture_loop_scope")
-    if not default_loop_scope:
+    default_fixture_loop_scope = config.getini("asyncio_default_fixture_loop_scope")
+    _validate_scope(default_fixture_loop_scope, "asyncio_default_fixture_loop_scope")
+    if not default_fixture_loop_scope:
         warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
+
+    default_test_loop_scope = config.getini("asyncio_default_test_loop_scope")
+    _validate_scope(default_test_loop_scope, "asyncio_default_test_loop_scope")
     config.addinivalue_line(
         "markers",
         "asyncio: "
diff --git a/tests/test_fixture_loop_scopes.py b/tests/test_fixture_loop_scopes.py
index a9ce4b35..95e46818 100644
--- a/tests/test_fixture_loop_scopes.py
+++ b/tests/test_fixture_loop_scopes.py
@@ -136,3 +136,20 @@ async def test_runs_in_fixture_loop(fixture_loop):
     )
     result = pytester.runpytest_subprocess("--asyncio-mode=strict")
     result.assert_outcomes(passed=1)
+
+
+def test_invalid_default_fixture_loop_scope_raises_error(pytester: Pytester):
+    pytester.makeini(
+        """\
+        [pytest]
+        asyncio_default_fixture_loop_scope = invalid_scope
+        """
+    )
+    result = pytester.runpytest()
+    result.stderr.fnmatch_lines(
+        [
+            "ERROR: 'invalid_scope' is not a valid "
+            "asyncio_default_fixture_loop_scope. Valid scopes are: "
+            "function, class, module, package, session."
+        ]
+    )