diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..b7b4487
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "vendor/openapi-schema-test-suite"]
+	path = vendor/openapi-schema-test-suite
+	url = https://github.com/python-openapi/openapi-schema-test-suite.git
diff --git a/pyproject.toml b/pyproject.toml
index 22db0f3..68c55a4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -80,6 +80,7 @@ classifiers = [
 ]
 include = [
     {path = "tests", format = "sdist"},
+    {path = "vendor/openapi-schema-test-suite/tests", format = "sdist"},
 ]
 
 [tool.poetry.dependencies]
diff --git a/tests/test_suite.py b/tests/test_suite.py
new file mode 100644
index 0000000..7bafbbf
--- /dev/null
+++ b/tests/test_suite.py
@@ -0,0 +1,196 @@
+"""
+Test runner for the openapi-schema-test-suite.
+
+This module integrates the external test suite from
+https://github.com/python-openapi/openapi-schema-test-suite
+to validate OAS 3.0, OAS 3.1 and OAS 3.2 schema validators against
+the canonical test cases.
+"""
+
+import json
+from pathlib import Path
+from typing import Any
+
+import pytest
+from jsonschema.exceptions import ValidationError
+
+from openapi_schema_validator import OAS30Validator
+from openapi_schema_validator import OAS31Validator
+from openapi_schema_validator import OAS32Validator
+from openapi_schema_validator import oas30_format_checker
+from openapi_schema_validator import oas31_format_checker
+from openapi_schema_validator import oas32_format_checker
+
+SUITE_ROOT = (
+    Path(__file__).parent.parent
+    / "vendor"
+    / "openapi-schema-test-suite"
+    / "tests"
+)
+
+# Each entry is (dialect, relative_path, case_description, test_description).
+_KNOWN_FAILURES: dict[tuple[str, str, str, str], str] = {
+    (
+        "oas30",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "a relative URI is not a valid URI",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas30",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "an invalid URI is not valid",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas31",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "a relative URI is not a valid URI",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas31",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "an invalid URI is not valid",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas32",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "a relative URI is not a valid URI",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas32",
+        "optional/format/format-assertion.json",
+        "format uri with assertion",
+        "an invalid URI is not valid",
+    ): "uri format checker does not validate RFC 3986 absolute-URI requirement",
+    (
+        "oas30",
+        "discriminator.json",
+        "discriminator as annotation",
+        "a cat object is valid",
+    ): "discriminator not fully supported in base oas30",
+    (
+        "oas30",
+        "discriminator.json",
+        "discriminator as annotation",
+        "a dog object is valid",
+    ): "discriminator not fully supported in base oas30",
+    (
+        "oas30",
+        "discriminator.json",
+        "discriminator with mapping",
+        "a car object is valid",
+    ): "discriminator mapping",
+    (
+        "oas30",
+        "discriminator.json",
+        "discriminator with mapping",
+        "a truck object is valid",
+    ): "discriminator mapping",
+    (
+        "oas30",
+        "ref.json",
+        "$ref sibling keywords are ignored",
+        "a short string is valid because minLength sibling is ignored",
+    ): "we do not ignore sibling keywords in oas30",
+    (
+        "oas30",
+        "type.json",
+        "integer type matches integers",
+        "a float with zero fractional part is an integer",
+    ): "float with zero fractional part",
+}
+
+_DIALECT_CONFIG: dict[str, dict[str, Any]] = {
+    "oas30": {
+        "validator_class": OAS30Validator,
+        "format_checker": oas30_format_checker,
+    },
+    "oas31": {
+        "validator_class": OAS31Validator,
+        "format_checker": oas31_format_checker,
+    },
+    "oas32": {
+        "validator_class": OAS32Validator,
+        "format_checker": oas32_format_checker,
+    },
+}
+
+
+def _collect_params() -> list[pytest.param]:
+    params: list[pytest.param] = []
+
+    for dialect, config in _DIALECT_CONFIG.items():
+        dialect_dir = SUITE_ROOT / dialect
+        if not dialect_dir.is_dir():
+            continue
+
+        for json_path in sorted(dialect_dir.rglob("*.json")):
+            rel_path = json_path.relative_to(dialect_dir)
+            is_in_optional_dir = rel_path.parts[0] == "optional"
+            format_checker = (
+                config["format_checker"] if is_in_optional_dir else None
+            )
+
+            test_cases: list[dict[str, Any]] = json.loads(
+                json_path.read_text(encoding="utf-8")
+            )
+            for case in test_cases:
+                case_desc: str = case["description"]
+                schema: dict[str, Any] = case["schema"]
+                for test in case["tests"]:
+                    test_desc: str = test["description"]
+                    data: Any = test["data"]
+                    expected_valid: bool = test["valid"]
+
+                    param_id = f"{dialect}/{rel_path}/{case_desc}/{test_desc}"
+                    failure_key = (
+                        dialect,
+                        str(rel_path),
+                        case_desc,
+                        test_desc,
+                    )
+                    marks: list[pytest.MarkDecorator] = []
+                    if failure_key in _KNOWN_FAILURES:
+                        marks.append(
+                            pytest.mark.xfail(
+                                reason=_KNOWN_FAILURES[failure_key],
+                                strict=True,
+                            )
+                        )
+                    params.append(
+                        pytest.param(
+                            config["validator_class"],
+                            schema,
+                            format_checker,
+                            data,
+                            expected_valid,
+                            id=param_id,
+                            marks=marks,
+                        )
+                    )
+
+    return params
+
+
+@pytest.mark.parametrize(
+    "validator_class,schema,format_checker,data,expected_valid",
+    _collect_params(),
+)
+def test_suite(
+    validator_class: Any,
+    schema: dict[str, Any],
+    format_checker: Any,
+    data: Any,
+    expected_valid: bool,
+) -> None:
+    validator = validator_class(schema, format_checker=format_checker)
+    errors = list(validator.iter_errors(data))
+    is_valid = len(errors) == 0
+    assert is_valid == expected_valid, (
+        f"Expected valid={expected_valid}, got valid={is_valid}. "
+        f"Errors: {[e.message for e in errors]}"
+    )
diff --git a/vendor/openapi-schema-test-suite b/vendor/openapi-schema-test-suite
new file mode 160000
index 0000000..741c876
--- /dev/null
+++ b/vendor/openapi-schema-test-suite
@@ -0,0 +1 @@
+Subproject commit 741c876969af3a3025dfea4a3f398da23e5e7251