diff --git a/sdks/implementations/python/README.md b/sdks/implementations/python/README.md
new file mode 100644
index 000000000..59f4068a0
--- /dev/null
+++ b/sdks/implementations/python/README.md
@@ -0,0 +1,27 @@
+# Stack Auth Python SDK
+
+Python SDK for [Stack Auth](https://stack-auth.com) - authentication, user management, and team management for your Python backend.
+
+## Installation
+
+```bash
+pip install stack-auth
+```
+
+## Quick Start
+
+```python
+from stack_auth import StackServerApp
+
+app = StackServerApp(
+    project_id="your-project-id",
+    secret_server_key="your-secret-key",
+)
+
+# Verify a request's access token
+user = await app.authenticate_request(request)
+```
+
+## Requirements
+
+- Python 3.10+
diff --git a/sdks/implementations/python/pyproject.toml b/sdks/implementations/python/pyproject.toml
new file mode 100644
index 000000000..87f064860
--- /dev/null
+++ b/sdks/implementations/python/pyproject.toml
@@ -0,0 +1,54 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "stack-auth"
+version = "0.1.0"
+description = "Python SDK for Stack Auth"
+readme = "README.md"
+license = "MIT"
+requires-python = ">=3.10"
+classifiers = [
+    "Development Status :: 3 - Alpha",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Typing :: Typed",
+]
+dependencies = [
+    "httpx>=0.27,<1.0",
+    "pyjwt[crypto]>=2.9,<3.0",
+    "pydantic>=2.7,<3.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.0",
+    "pytest-asyncio>=1.0",
+    "respx>=0.22",
+    "ruff>=0.11",
+    "mypy>=1.10",
+    "pytest-cov>=5.0",
+]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/stack_auth"]
+
+[tool.ruff]
+target-version = "py310"
+line-length = 120
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "N", "UP", "B", "SIM", "TCH"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+
+[tool.mypy]
+python_version = "3.10"
+strict = true
diff --git a/sdks/implementations/python/src/stack_auth/__init__.py b/sdks/implementations/python/src/stack_auth/__init__.py
new file mode 100644
index 000000000..83040623b
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/__init__.py
@@ -0,0 +1 @@
+# Placeholder - will be populated after errors.py is implemented
diff --git a/sdks/implementations/python/src/stack_auth/_constants.py b/sdks/implementations/python/src/stack_auth/_constants.py
new file mode 100644
index 000000000..a07fcc0ad
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/_constants.py
@@ -0,0 +1,3 @@
+DEFAULT_BASE_URL = "https://api.stack-auth.com"
+SDK_NAME = "python"
+API_VERSION = "v1"
diff --git a/sdks/implementations/python/src/stack_auth/_types.py b/sdks/implementations/python/src/stack_auth/_types.py
new file mode 100644
index 000000000..db6bb5fd3
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/_types.py
@@ -0,0 +1,8 @@
+from __future__ import annotations
+
+from typing import Mapping, Protocol
+
+
+class RequestLike(Protocol):
+    @property
+    def headers(self) -> Mapping[str, str]: ...
diff --git a/sdks/implementations/python/src/stack_auth/_version.py b/sdks/implementations/python/src/stack_auth/_version.py
new file mode 100644
index 000000000..3dc1f76bc
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/_version.py
@@ -0,0 +1 @@
+__version__ = "0.1.0"
diff --git a/sdks/implementations/python/src/stack_auth/errors.py b/sdks/implementations/python/src/stack_auth/errors.py
new file mode 100644
index 000000000..61b6c2d23
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/errors.py
@@ -0,0 +1 @@
+# Placeholder - error hierarchy not yet implemented
diff --git a/sdks/implementations/python/src/stack_auth/models/__init__.py b/sdks/implementations/python/src/stack_auth/models/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/sdks/implementations/python/src/stack_auth/models/_base.py b/sdks/implementations/python/src/stack_auth/models/_base.py
new file mode 100644
index 000000000..203d61c6e
--- /dev/null
+++ b/sdks/implementations/python/src/stack_auth/models/_base.py
@@ -0,0 +1 @@
+# Placeholder - base model not yet implemented
diff --git a/sdks/implementations/python/src/stack_auth/py.typed b/sdks/implementations/python/src/stack_auth/py.typed
new file mode 100644
index 000000000..e69de29bb
diff --git a/sdks/implementations/python/tests/__init__.py b/sdks/implementations/python/tests/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/sdks/implementations/python/tests/conftest.py b/sdks/implementations/python/tests/conftest.py
new file mode 100644
index 000000000..def615cb8
--- /dev/null
+++ b/sdks/implementations/python/tests/conftest.py
@@ -0,0 +1,6 @@
+import pytest
+
+
+@pytest.fixture
+def base_url() -> str:
+    return "https://api.stack-auth.com"
diff --git a/sdks/implementations/python/tests/test_errors.py b/sdks/implementations/python/tests/test_errors.py
new file mode 100644
index 000000000..0ba82a563
--- /dev/null
+++ b/sdks/implementations/python/tests/test_errors.py
@@ -0,0 +1,187 @@
+"""Tests for the Stack Auth error hierarchy and from_response() dispatch."""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+import pytest
+
+from stack_auth.errors import (
+    AnalyticsError,
+    ApiKeyError,
+    AuthenticationError,
+    CliError,
+    ConflictError,
+    EmailError,
+    NotFoundError,
+    OAuthError,
+    PasskeyError,
+    PaymentError,
+    PermissionDeniedError,
+    RateLimitError,
+    StackAuthError,
+    ValidationError,
+)
+from stack_auth.models._base import StackAuthModel
+
+
+class TestStackAuthErrorBasics:
+    """Test StackAuthError base class storage and string representation."""
+
+    def test_stores_code_and_message(self) -> None:
+        err = StackAuthError("CODE", "msg")
+        assert err.code == "CODE"
+        assert err.message == "msg"
+
+    def test_str_contains_code_and_message(self) -> None:
+        err = StackAuthError("CODE", "msg")
+        s = str(err)
+        assert "CODE" in s
+        assert "msg" in s
+
+    def test_stores_details(self) -> None:
+        err = StackAuthError("CODE", "msg", {"key": "val"})
+        assert err.details == {"key": "val"}
+
+    def test_details_default_none(self) -> None:
+        err = StackAuthError("CODE", "msg")
+        assert err.details is None
+
+
+class TestErrorSubclasses:
+    """Test that all category subclasses exist and inherit from StackAuthError."""
+
+    @pytest.mark.parametrize(
+        "cls",
+        [
+            AuthenticationError,
+            NotFoundError,
+            ValidationError,
+            PermissionDeniedError,
+            ConflictError,
+            OAuthError,
+            PasskeyError,
+            ApiKeyError,
+            PaymentError,
+            EmailError,
+            RateLimitError,
+            CliError,
+            AnalyticsError,
+        ],
+    )
+    def test_is_subclass_of_stack_auth_error(self, cls: type) -> None:
+        assert issubclass(cls, StackAuthError)
+
+    @pytest.mark.parametrize(
+        "cls",
+        [
+            AuthenticationError,
+            NotFoundError,
+            ValidationError,
+            PermissionDeniedError,
+            ConflictError,
+            OAuthError,
+            PasskeyError,
+            ApiKeyError,
+            PaymentError,
+            EmailError,
+            RateLimitError,
+            CliError,
+            AnalyticsError,
+        ],
+    )
+    def test_can_be_caught_with_except_stack_auth_error(self, cls: type) -> None:
+        with pytest.raises(StackAuthError):
+            raise cls("TEST_CODE", "test message")
+
+
+class TestFromResponse:
+    """Test from_response() factory dispatch for known and unknown codes."""
+
+    def test_invalid_access_token_returns_authentication_error(self) -> None:
+        err = StackAuthError.from_response("INVALID_ACCESS_TOKEN", "bad token")
+        assert isinstance(err, AuthenticationError)
+        assert err.code == "INVALID_ACCESS_TOKEN"
+        assert err.message == "bad token"
+
+    def test_user_not_found_returns_not_found_error(self) -> None:
+        err = StackAuthError.from_response("USER_NOT_FOUND", "no user")
+        assert isinstance(err, NotFoundError)
+
+    def test_schema_error_returns_validation_error(self) -> None:
+        err = StackAuthError.from_response("SCHEMA_ERROR", "bad schema")
+        assert isinstance(err, ValidationError)
+
+    def test_team_permission_required_returns_permission_error(self) -> None:
+        err = StackAuthError.from_response("TEAM_PERMISSION_REQUIRED", "denied")
+        assert isinstance(err, PermissionDeniedError)
+
+    def test_team_already_exists_returns_conflict_error(self) -> None:
+        err = StackAuthError.from_response("TEAM_ALREADY_EXISTS", "conflict")
+        assert isinstance(err, ConflictError)
+
+    def test_oauth_connection_not_connected_returns_oauth_error(self) -> None:
+        err = StackAuthError.from_response("OAUTH_CONNECTION_NOT_CONNECTED_TO_USER", "no conn")
+        assert isinstance(err, OAuthError)
+
+    def test_passkey_authentication_failed_returns_passkey_error(self) -> None:
+        err = StackAuthError.from_response("PASSKEY_AUTHENTICATION_FAILED", "failed")
+        assert isinstance(err, PasskeyError)
+
+    def test_api_key_not_valid_returns_api_key_error(self) -> None:
+        err = StackAuthError.from_response("API_KEY_NOT_VALID", "invalid")
+        assert isinstance(err, ApiKeyError)
+
+    def test_product_already_granted_returns_payment_error(self) -> None:
+        err = StackAuthError.from_response("PRODUCT_ALREADY_GRANTED", "granted")
+        assert isinstance(err, PaymentError)
+
+    def test_email_rendering_error_returns_email_error(self) -> None:
+        err = StackAuthError.from_response("EMAIL_RENDERING_ERROR", "render fail")
+        assert isinstance(err, EmailError)
+
+    def test_unknown_code_returns_base_stack_auth_error(self) -> None:
+        err = StackAuthError.from_response("TOTALLY_UNKNOWN_CODE", "surprise")
+        assert type(err) is StackAuthError
+        assert err.code == "TOTALLY_UNKNOWN_CODE"
+        assert err.message == "surprise"
+
+    def test_from_response_preserves_details(self) -> None:
+        err = StackAuthError.from_response("USER_NOT_FOUND", "no user", {"user_id": "abc"})
+        assert err.details == {"user_id": "abc"}
+
+    def test_cli_auth_error_returns_cli_error(self) -> None:
+        err = StackAuthError.from_response("CLI_AUTH_ERROR", "cli fail")
+        assert isinstance(err, CliError)
+
+    def test_analytics_query_timeout_returns_analytics_error(self) -> None:
+        err = StackAuthError.from_response("ANALYTICS_QUERY_TIMEOUT", "timeout")
+        assert isinstance(err, AnalyticsError)
+
+
+class TestErrorCodeMapCoverage:
+    """Test that the error code map has comprehensive coverage."""
+
+    def test_error_code_map_has_at_least_90_entries(self) -> None:
+        from stack_auth.errors import _ERROR_CODE_MAP
+
+        assert len(_ERROR_CODE_MAP) >= 90, f"Expected >= 90 entries, got {len(_ERROR_CODE_MAP)}"
+
+
+class TestStackAuthModel:
+    """Test the StackAuthModel base class."""
+
+    def test_model_config_populate_by_name(self) -> None:
+        assert StackAuthModel.model_config.get("populate_by_name") is True
+
+    def test_model_config_extra_ignore(self) -> None:
+        assert StackAuthModel.model_config.get("extra") == "ignore"
+
+    def test_millis_to_datetime_converts_correctly(self) -> None:
+        result = StackAuthModel._millis_to_datetime(1711296000000)
+        expected = datetime(2024, 3, 24, 16, 0, tzinfo=timezone.utc)
+        assert result == expected
+
+    def test_millis_to_datetime_none_returns_none(self) -> None:
+        result = StackAuthModel._millis_to_datetime(None)
+        assert result is None