diff --git a/openapi_spec_validator/handlers/compat.py b/openapi_spec_validator/handlers/compat.py
index 534e746..9451a7d 100644
--- a/openapi_spec_validator/handlers/compat.py
+++ b/openapi_spec_validator/handlers/compat.py
@@ -4,5 +4,36 @@
 except ImportError:
     from yaml import SafeLoader
 
+from jsonschema.exceptions import ValidationError
 
-__all__ = ['SafeLoader', ]
+
+class UniqueSchemasLoader(SafeLoader):
+    """Loader that checks that schemas definitions are unique"""
+
+    POSSIBLE_SCHEMAS_YAML_PATHS = ["definitions", "components.schemas"]
+
+    def construct_mapping(self, node, deep=True):
+        self._check_for_duplicate_schemas_definitions(node, deep, self.POSSIBLE_SCHEMAS_YAML_PATHS)
+        return super().construct_mapping(node, deep)
+
+    def _check_for_duplicate_schemas_definitions(self, node, deep, possible_schemas_yaml_paths):
+        for schemas_yaml_path in possible_schemas_yaml_paths:
+            keys = []
+            for key_node, value_node in node.value:
+                if schemas_yaml_path:
+                    if key_node.value == schemas_yaml_path.split(".")[0]:
+                        return self._check_for_duplicate_schemas_definitions(
+                            value_node,
+                            deep,
+                            possible_schemas_yaml_paths=[
+                                ".".join(schemas_yaml_path.split(".")[1:])
+                            ],
+                        )
+                else:
+                    key = self.construct_object(key_node, deep=deep)
+                    if key in keys:
+                        raise ValidationError(f"Duplicate definition for {key} schema.")
+                    keys.append(key)
+
+
+__all__ = ["SafeLoader", "UniqueSchemasLoader"]
diff --git a/openapi_spec_validator/handlers/file.py b/openapi_spec_validator/handlers/file.py
index 7c3ea65..f46a4d0 100644
--- a/openapi_spec_validator/handlers/file.py
+++ b/openapi_spec_validator/handlers/file.py
@@ -5,14 +5,14 @@
 from yaml import load
 
 from openapi_spec_validator.handlers.base import BaseHandler
-from openapi_spec_validator.handlers.compat import SafeLoader
+from openapi_spec_validator.handlers.compat import UniqueSchemasLoader
 from openapi_spec_validator.handlers.utils import uri_to_path
 
 
 class FileObjectHandler(BaseHandler):
     """OpenAPI spec validator file-like object handler."""
 
-    def __init__(self, loader=SafeLoader):
+    def __init__(self, loader=UniqueSchemasLoader):
         self.loader = loader
 
     def __call__(self, f):
diff --git a/tests/integration/data/v2.0/petstore_duplicate_schemas_def.yaml b/tests/integration/data/v2.0/petstore_duplicate_schemas_def.yaml
new file mode 100644
index 0000000..4206c54
--- /dev/null
+++ b/tests/integration/data/v2.0/petstore_duplicate_schemas_def.yaml
@@ -0,0 +1,113 @@
+swagger: "2.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+host: petstore.swagger.io
+basePath: /v1
+schemes:
+  - http
+consumes:
+  - application/json
+produces:
+  - application/json
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      tags:
+        - pets
+      parameters:
+        - name: limit
+          in: query
+          description: How many items to return at one time (max 100)
+          required: false
+          type: integer
+          format: int32
+      responses:
+        200:
+          description: A paged array of pets
+          headers:
+            x-next:
+              type: string
+              description: A link to the next page of responses
+          schema:
+            $ref: '#/definitions/Pets'
+        default:
+          description: unexpected error
+          schema:
+            $ref: '#/definitions/Error'
+    post:
+      summary: Create a pet
+      operationId: createPets
+      tags:
+        - pets
+      responses:
+        '201':
+          description: Null response
+        default:
+          description: unexpected error
+          schema:
+            $ref: '#/definitions/Error'
+  /pets/{petId}:
+    get:
+      summary: Info for a specific pet
+      operationId: showPetById
+      tags:
+        - pets
+      parameters:
+        - name: petId
+          in: path
+          required: true
+          description: The id of the pet to retrieve
+          type: string
+      responses:
+        '200':
+          description: Expected response to a valid request
+          schema:
+            $ref: '#/definitions/Pets'
+        default:
+          description: unexpected error
+          schema:
+            $ref: '#/definitions/Error'
+definitions:
+  Pet:
+    required:
+      - id
+      - name
+    properties:
+      id:
+        type: integer
+        format: int64
+      name:
+        type: string
+      tag:
+        type: string
+  Pet:
+    required:
+      - id
+      - name
+    properties:
+      id:
+        type: integer
+        format: int64
+      name:
+        type: string
+      tag:
+        type: string
+  Pets:
+    type: array
+    items:
+      $ref: '#/definitions/Pet'
+  Error:
+    required:
+      - code
+      - message
+    properties:
+      code:
+        type: integer
+        format: int32
+      message:
+        type: string
diff --git a/tests/integration/data/v3.0/petstore_duplicate_schemas_def.yaml b/tests/integration/data/v3.0/petstore_duplicate_schemas_def.yaml
new file mode 100644
index 0000000..4452bf3
--- /dev/null
+++ b/tests/integration/data/v3.0/petstore_duplicate_schemas_def.yaml
@@ -0,0 +1,115 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+servers:
+  - url: http://petstore.swagger.io/v1
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      tags:
+        - pets
+      parameters:
+        - name: limit
+          in: query
+          description: How many items to return at one time (max 100)
+          required: false
+          schema:
+            type: integer
+            format: int32
+      responses:
+        200:
+          description: An paged array of pets
+          headers:
+            x-next:
+              description: A link to the next page of responses
+              schema:
+                type: string
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+    post:
+      summary: Create a pet
+      operationId: createPets
+      tags:
+        - pets
+      responses:
+        '201':
+          description: Null response
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+  /pets/{petId}:
+    get:
+      summary: Info for a specific pet
+      operationId: showPetById
+      tags:
+        - pets
+      parameters:
+        - name: petId
+          in: path
+          required: true
+          description: The id of the pet to retrieve
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Expected response to a valid request
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+components:
+  schemas:
+    Pet:
+      required:
+        - id
+        - name
+      properties:
+        id:
+          type: integer
+          format: int64
+        name:
+          type: string
+        tag:
+          type: string
+        $ref:
+          type: string
+    Pets:
+      type: array
+      items:
+        $ref: "#/components/schemas/Pet"
+    Pets:
+      type: array
+      items:
+        $ref: "#/components/schemas/Pet"
+    Error:
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: integer
+          format: int32
+        message:
+          type: string
diff --git a/tests/integration/data/v3.1/petstore_duplicate_schemas_def.yaml b/tests/integration/data/v3.1/petstore_duplicate_schemas_def.yaml
new file mode 100644
index 0000000..2fe2ff8
--- /dev/null
+++ b/tests/integration/data/v3.1/petstore_duplicate_schemas_def.yaml
@@ -0,0 +1,122 @@
+openapi: "3.1.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT License
+    identifier: MIT
+servers:
+  - url: http://petstore.swagger.io/v1
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      tags:
+        - pets
+      parameters:
+        - name: limit
+          in: query
+          description: How many items to return at one time (max 100)
+          required: false
+          schema:
+            type: integer
+            format: int32
+      responses:
+        200:
+          description: An paged array of pets
+          headers:
+            x-next:
+              description: A link to the next page of responses
+              schema:
+                type: string
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+    post:
+      summary: Create a pet
+      operationId: createPets
+      tags:
+        - pets
+      responses:
+        '201':
+          description: Null response
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+  /pets/{petId}:
+    get:
+      summary: Info for a specific pet
+      operationId: showPetById
+      tags:
+        - pets
+      parameters:
+        - name: petId
+          in: path
+          required: true
+          description: The id of the pet to retrieve
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Expected response to a valid request
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+components:
+  schemas:
+    Pet:
+      required:
+        - id
+        - name
+      properties:
+        id:
+          type: integer
+          format: int64
+        name:
+          type: string
+        tag:
+          type: string
+        $ref:
+          type: string
+    Pets:
+      type: array
+      items:
+        $ref: "#/components/schemas/Pet"
+    Error:
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: integer
+          format: int32
+        message:
+          type: string
+    Error:
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: integer
+          format: int32
+        message:
+          type: string
diff --git a/tests/integration/test_main.py b/tests/integration/test_main.py
index a99f4f7..15236e2 100644
--- a/tests/integration/test_main.py
+++ b/tests/integration/test_main.py
@@ -1,51 +1,45 @@
-import pytest
 from io import StringIO
+from unittest import mock
 
-from openapi_spec_validator.__main__ import main
+import pytest
 
-from unittest import mock
+from openapi_spec_validator.__main__ import main
 
 
 def test_schema_default():
     """Test default schema is 3.1.0"""
-    testargs = ['./tests/integration/data/v3.1/petstore.yaml']
+    testargs = ["./tests/integration/data/v3.1/petstore.yaml"]
     main(testargs)
 
 
 def test_schema_v31():
     """No errors when calling proper v3.1 file."""
-    testargs = ['--schema', '3.1.0',
-                './tests/integration/data/v3.1/petstore.yaml']
+    testargs = ["--schema", "3.1.0", "./tests/integration/data/v3.1/petstore.yaml"]
     main(testargs)
 
 
 def test_schema_v30():
     """No errors when calling proper v3.0 file."""
-    testargs = ['--schema', '3.0.0',
-                './tests/integration/data/v3.0/petstore.yaml']
+    testargs = ["--schema", "3.0.0", "./tests/integration/data/v3.0/petstore.yaml"]
     main(testargs)
 
 
 def test_schema_v2():
     """No errors when calling with proper v2 file."""
-    testargs = ['--schema', '2.0',
-                './tests/integration/data/v2.0/petstore.yaml']
+    testargs = ["--schema", "2.0", "./tests/integration/data/v2.0/petstore.yaml"]
     main(testargs)
 
 
 def test_errors_on_missing_description_best(capsys):
     """An error is obviously printed given an empty schema."""
-    testargs = [
-        './tests/integration/data/v3.0/missing-description.yaml',
-        '--schema=3.0.0'
-    ]
+    testargs = ["./tests/integration/data/v3.0/missing-description.yaml", "--schema=3.0.0"]
     with pytest.raises(SystemExit):
         main(testargs)
     out, err = capsys.readouterr()
     assert "Failed validating" in out
     assert "'description' is a required property" in out
     assert "'$ref' is a required property" not in out
-    assert '1 more subschemas errors' in out
+    assert "1 more subschemas errors" in out
 
 
 def test_errors_on_missing_description_full(capsys):
@@ -61,51 +55,63 @@ def test_errors_on_missing_description_full(capsys):
     assert "Failed validating" in out
     assert "'description' is a required property" in out
     assert "'$ref' is a required property" in out
-    assert '1 more subschema error' not in out
+    assert "1 more subschema error" not in out
 
 
 def test_schema_unknown():
     """Errors on running with unknown schema."""
-    testargs = ['--schema', 'x.x',
-                './tests/integration/data/v2.0/petstore.yaml']
+    testargs = ["--schema", "x.x", "./tests/integration/data/v2.0/petstore.yaml"]
     with pytest.raises(SystemExit):
         main(testargs)
 
 
 def test_validation_error():
     """SystemExit on running with ValidationError."""
-    testargs = ['--schema', '3.0.0',
-                './tests/integration/data/v2.0/petstore.yaml']
+    testargs = ["--schema", "3.0.0", "./tests/integration/data/v2.0/petstore.yaml"]
     with pytest.raises(SystemExit):
         main(testargs)
 
 
 @mock.patch(
-    'openapi_spec_validator.__main__.openapi_v30_spec_validator.validate',
+    "openapi_spec_validator.__main__.openapi_v30_spec_validator.validate",
     side_effect=Exception,
 )
 def test_unknown_error(m_validate):
     """SystemExit on running with unknown error."""
-    testargs = ['--schema', '3.0.0',
-                './tests/integration/data/v2.0/petstore.yaml']
+    testargs = ["--schema", "3.0.0", "./tests/integration/data/v2.0/petstore.yaml"]
     with pytest.raises(SystemExit):
         main(testargs)
 
 
 def test_nonexisting_file():
     """Calling with non-existing file should sys.exit."""
-    testargs = ['i_dont_exist.yaml']
+    testargs = ["i_dont_exist.yaml"]
     with pytest.raises(SystemExit):
         main(testargs)
 
 
 def test_schema_stdin():
     """Test schema from STDIN"""
-    spes_path = './tests/integration/data/v3.0/petstore.yaml'
-    with open(spes_path, 'r') as spec_file:
+    spes_path = "./tests/integration/data/v3.0/petstore.yaml"
+    with open(spes_path, "r") as spec_file:
         spec_lines = spec_file.readlines()
     spec_io = StringIO("".join(spec_lines))
 
-    testargs = ['--schema', '3.0.0', '-']
-    with mock.patch('openapi_spec_validator.__main__.sys.stdin', spec_io):
+    testargs = ["--schema", "3.0.0", "-"]
+    with mock.patch("openapi_spec_validator.__main__.sys.stdin", spec_io):
+        main(testargs)
+
+
+@pytest.mark.parametrize(
+    "version,spec_path",
+    [
+        ("3.1.0", "./tests/integration/data/v3.1/petstore_duplicate_schemas_def.yaml"),
+        ("3.0.0", "./tests/integration/data/v3.0/petstore_duplicate_schemas_def.yaml"),
+        ("2.0", "./tests/integration/data/v2.0/petstore_duplicate_schemas_def.yaml"),
+    ],
+)
+def test_duplicate_schemas_definition(version, spec_path):
+    """Test exception when Swagger has duplicate schema definitions"""
+    testargs = ["--schema", version, spec_path]
+    with pytest.raises(SystemExit):
         main(testargs)

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