diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
index b08a6f518719..0a061f851be3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
@@ -1119,6 +1119,10 @@ private ModelsMap postProcessModelsMap(ModelsMap objs) {
                     readOnlyFields.add(cp.name);
                 }
 
+                if (cp.vendorExtensions.containsKey("x-python-not-string-enum-values")) {
+                    moduleImports.add(PYDANTIC, "field_validator");
+                }
+
                 String typing = pydantic.generatePythonType(cp);
                 cp.vendorExtensions.put(X_PY_TYPING, typing);
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
index 61936225db59..b466306749da 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
@@ -1032,6 +1032,20 @@ public void postProcessParameter(CodegenParameter parameter) {
     @Override
     public void postProcessModelProperty(CodegenModel model, CodegenProperty property) {
         super.postProcessModelProperty(model, property);
+
+        if (property.getComposedSchemas() != null
+                && property.getComposedSchemas().getNot() != null) {
+            CodegenProperty notProperty = property.getComposedSchemas().getNot();
+            if (notProperty.isEnum
+                    && notProperty.isString
+                    && notProperty.allowableValues != null
+                    && notProperty.allowableValues.get("values") != null) {
+                property.vendorExtensions.put(
+                        "x-python-not-string-enum-values",
+                        notProperty.allowableValues.get("values"));
+            }
+        }
+
         if (hasOneOf(model) || hasAnyOf(model)) {
             return;
         }
diff --git a/modules/openapi-generator/src/main/resources/python/model_generic.mustache b/modules/openapi-generator/src/main/resources/python/model_generic.mustache
index 3d1758ac7ec6..67ee274208cf 100644
--- a/modules/openapi-generator/src/main/resources/python/model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/python/model_generic.mustache
@@ -133,6 +133,26 @@ https://github.com/OpenAPITools/openapi-generator/blob/c84b949df1a9ec04ba75989cb
         {{/isContainer}}
         return value
     {{/isEnum}}
+    {{#vendorExtensions.x-python-not-string-enum-values.size}}
+    @field_validator('{{{name}}}')
+    def {{{name}}}_validate_not_enum(cls, value):
+        """Validates values excluded by not"""
+        {{^required}}
+        if value is None:
+            return value
+
+        {{/required}}
+        {{#required}}
+        {{#isNullable}}
+        if value is None:
+            return value
+
+        {{/isNullable}}
+        {{/required}}
+        if value in set([{{#vendorExtensions.x-python-not-string-enum-values}}{{#lambda.pythonStringLiteral}}{{{.}}}{{/lambda.pythonStringLiteral}}{{^-last}}, {{/-last}}{{/vendorExtensions.x-python-not-string-enum-values}}]):
+            raise ValueError("must not be one of excluded enum values")
+        return value
+    {{/vendorExtensions.x-python-not-string-enum-values.size}}
 {{/vars}}
 
 {{#vendorExtensions.x-py-preprocesses-input-names}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java
index 7ae88fae560b..9fb6172292bb 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java
@@ -142,6 +142,39 @@ public void testInitialConfigValues() throws Exception {
         Assert.assertNull(codegen.additionalProperties().get(CodegenConstants.SOURCE_FOLDER));
     }
 
+    @Test
+    public void testOneOfNotEnumValidation() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("python")
+                .setInputSpec("src/test/resources/3_1/python/oneof-not-enum.yaml")
+                .setOutputDir(output.getAbsolutePath());
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        Path other = Paths.get(
+                output.getAbsolutePath(),
+                "openapi_client",
+                "models",
+                "other.py");
+
+        String otherContent = Files.readString(other);
+
+        Assert.assertTrue(otherContent.contains(
+                "if value in set([\"known\", \"reserved\"]):"));
+        Assert.assertTrue(otherContent.contains(
+                "raise ValueError(\"must not be one of excluded enum values\")"));
+        Assert.assertTrue(otherContent.contains("@field_validator('kind')"));
+
+        Assert.assertEquals(
+                otherContent.split("def kind_validate_not_enum", -1).length - 1,
+                1);
+    }
+
     @Test
     public void testSettersForConfigValues() throws Exception {
         final PythonClientCodegen codegen = new PythonClientCodegen();
diff --git a/modules/openapi-generator/src/test/resources/3_1/python/oneof-not-enum.yaml b/modules/openapi-generator/src/test/resources/3_1/python/oneof-not-enum.yaml
new file mode 100644
index 000000000000..baee94e2394e
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_1/python/oneof-not-enum.yaml
@@ -0,0 +1,36 @@
+openapi: 3.1.0
+
+info:
+  title: oneOf not enum repro
+  version: 1.0.0
+
+paths: {}
+
+components:
+  schemas:
+    Known:
+      type: object
+      required:
+        - kind
+      properties:
+        kind:
+          type: string
+          enum:
+            - known
+
+    Other:
+      type: object
+      required:
+        - kind
+      properties:
+        kind:
+          type: string
+          not:
+            enum:
+              - known
+              - reserved
+
+    TaggedUnion:
+      oneOf:
+        - $ref: '#/components/schemas/Known'
+        - $ref: '#/components/schemas/Other'