diff --git a/.env.example b/.env.example
new file mode 100644
index 00000000..d71942da
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,15 @@
+# Google
+GOOGLE_CLIENT_ID=your_google_client_id
+GOOGLE_CLIENT_SECRET=your_google_client_secret
+
+# GitHub
+GITHUB_CLIENT_ID=your_github_client_id
+GITHUB_CLIENT_SECRET=your_github_client_secret
+
+# Microsoft
+MICROSOFT_CLIENT_ID=your_microsoft_client_id
+MICROSOFT_CLIENT_SECRET=your_microsoft_client_secret
+
+# General
+SECRET_KEY=supersecret
+BASE_URL=http://localhost:5000
diff --git a/gramps_webapi/app.py b/gramps_webapi/app.py
index 2041c2a1..86107e4b 100644
--- a/gramps_webapi/app.py
+++ b/gramps_webapi/app.py
@@ -17,13 +17,13 @@
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 
-"""Flask web app providing a REST API to a Gramps family tree."""
 
 import logging
 import os
 import warnings
 from typing import Any, Dict, Optional
 
+
 from flask import Flask, abort, g, send_from_directory
 from flask_compress import Compress
 from flask_cors import CORS
@@ -31,12 +31,14 @@
 from gramps.gen.config import config as gramps_config
 from gramps.gen.config import set as setconfig
 
+
 from .api import api_blueprint
-from .api.cache import request_cache, thumbnail_cache
+from .api.cache import thumbnail_cache, request_cache
 from .api.ratelimiter import limiter
 from .api.search.embeddings import load_model
 from .api.util import close_db
 from .auth import user_db
+from .auth.oidc import configure_oauth, oidc_bp
 from .config import DefaultConfig, DefaultConfigJWT
 from .const import API_PREFIX, ENV_CONFIG_FILE, TREE_MULTI
 from .dbmanager import WebDbManager
@@ -49,20 +51,10 @@ def deprecated_config_from_env(app):
     This function will be removed eventually!
     """
     options = [
-        "TREE",
-        "SECRET_KEY",
-        "USER_DB_URI",
-        "POSTGRES_USER",
-        "POSTGRES_PASSWORD",
-        "MEDIA_BASE_DIR",
-        "SEARCH_INDEX_DIR",
-        "EMAIL_HOST",
-        "EMAIL_PORT",
-        "EMAIL_HOST_USER",
-        "EMAIL_HOST_PASSWORD",
-        "DEFAULT_FROM_EMAIL",
-        "BASE_URL",
-        "STATIC_PATH",
+        "TREE", "SECRET_KEY", "USER_DB_URI", "POSTGRES_USER", "POSTGRES_PASSWORD",
+        "MEDIA_BASE_DIR", "SEARCH_INDEX_DIR", "EMAIL_HOST", "EMAIL_PORT",
+        "EMAIL_HOST_USER", "EMAIL_HOST_PASSWORD", "DEFAULT_FROM_EMAIL",
+        "BASE_URL", "STATIC_PATH",
     ]
     for option in options:
         value = os.getenv(option)
@@ -79,7 +71,6 @@ def deprecated_config_from_env(app):
 def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool = True):
     """Flask application factory."""
     app = Flask(__name__)
-
     app.logger.setLevel(logging.INFO)
 
     # load default config
@@ -89,7 +80,7 @@ def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool =
     if os.getenv(ENV_CONFIG_FILE):
         app.config.from_envvar(ENV_CONFIG_FILE)
 
-    # use unprefixed environment variables if exist - deprecated!
+ # use unprefixed environment variables if exist - deprecated!
     deprecated_config_from_env(app)
 
     # use prefixed environment variables if exist
@@ -111,9 +102,11 @@ def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool =
     if db_path := os.getenv("GRAMPS_DATABASE_PATH"):
         setconfig("database.path", db_path)
 
+
     if app.config.get("LOG_LEVEL"):
         app.logger.setLevel(app.config["LOG_LEVEL"])
 
+
     if app.config["TREE"] != TREE_MULTI:
         # create database if missing (only in single-tree mode)
         WebDbManager(
@@ -122,6 +115,7 @@ def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool =
             ignore_lock=app.config["IGNORE_DB_LOCK"],
         )
 
+
     if app.config["TREE"] == TREE_MULTI and not app.config["MEDIA_PREFIX_TREE"]:
         warnings.warn(
             "You have enabled multi-tree support, but `MEDIA_PREFIX_TREE` is "
@@ -129,24 +123,31 @@ def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool =
             "files to users belonging to different trees!"
         )
 
+
     if app.config["TREE"] == TREE_MULTI and app.config["NEW_DB_BACKEND"] != "sqlite":
-        # needed in case a new postgres tree is to be created
+                # needed in case a new postgres tree is to be created
         gramps_config.set("database.host", app.config["POSTGRES_HOST"])
         gramps_config.set("database.port", str(app.config["POSTGRES_PORT"]))
 
     # load JWT default settings
     app.config.from_object(DefaultConfigJWT)
-
-    # instantiate JWT manager
     JWTManager(app)
 
+
     app.config["SQLALCHEMY_DATABASE_URI"] = app.config["USER_DB_URI"]
     user_db.init_app(app)
 
+
     request_cache.init_app(app, config=app.config["REQUEST_CACHE_CONFIG"])
+
+
+    configure_oauth(app)
+    app.register_blueprint(oidc_bp)
+
+
     thumbnail_cache.init_app(app, config=app.config["THUMBNAIL_CACHE_CONFIG"])
 
-    # enable CORS for /api/... resources
+# enable CORS for /api/... resources
     if app.config.get("CORS_ORIGINS"):
         CORS(
             app,
@@ -156,13 +157,15 @@ def create_app(config: Optional[Dict[str, Any]] = None, config_from_env: bool =
     # enable gzip compression
     Compress(app)
 
+
     static_path = app.config.get("STATIC_PATH")
 
-    # routes for static hosting (e.g. SPA frontend)
+ # routes for static hosting (e.g. SPA frontend)
     @app.route("/", methods=["GET", "POST"])
     def send_index():
         return send_from_directory(static_path, "index.html")
 
+
     @app.route("/<path:path>", methods=["GET", "POST"])
     def send_static(path):
         if path.startswith(API_PREFIX[1:]):
@@ -176,10 +179,11 @@ def send_static(path):
     # register the API blueprint
     app.register_blueprint(api_blueprint)
     limiter.init_app(app)
-
+    
     # instantiate celery
     create_celery(app)
 
+
     @app.teardown_appcontext
     def close_db_connection(exception) -> None:
         """Close the Gramps database after every request."""
@@ -190,6 +194,7 @@ def close_db_connection(exception) -> None:
         if db_write:
             close_db(db_write)
 
+
     @app.teardown_request
     def close_user_db_connection(exception) -> None:
         """Close the user database after every request."""
@@ -198,13 +203,16 @@ def close_user_db_connection(exception) -> None:
         user_db.session.close()  # pylint: disable=no-member
         user_db.session.remove()  # pylint: disable=no-member
 
+
     if app.config.get("VECTOR_EMBEDDING_MODEL"):
         app.config["_INITIALIZED_VECTOR_EMBEDDING_MODEL"] = load_model(
             app.config["VECTOR_EMBEDDING_MODEL"]
         )
 
+
     @app.route("/ready", methods=["GET"])
     def ready():
         return {"status": "ready"}, 200
 
+
     return app
diff --git a/gramps_webapi/auth/oidc.py b/gramps_webapi/auth/oidc.py
new file mode 100644
index 00000000..1a4db580
--- /dev/null
+++ b/gramps_webapi/auth/oidc.py
@@ -0,0 +1,156 @@
+import uuid
+from authlib.integrations.flask_client import OAuth
+from flask import Blueprint, redirect, url_for, request, current_app, jsonify
+from flask_jwt_extended import create_access_token, create_refresh_token
+from sqlalchemy.exc import IntegrityError
+
+
+from . import user_db, User, add_user
+from .const import ROLE_USER
+from ..api.util import get_tree_id, abort_with_message, tree_exists
+from ..api.auth import get_permissions
+from ..const import TREE_MULTI
+
+
+oauth = OAuth()
+oidc_bp = Blueprint("oidc", __name__, url_prefix="/auth")
+
+
+def configure_oauth(app):
+    if not app.config.get("OAUTH_ENABLED", False):
+        return
+
+
+    oauth.init_app(app)
+
+
+    if app.config.get("OAUTH_GOOGLE_CLIENT_ID") and app.config.get("OAUTH_GOOGLE_CLIENT_SECRET"):
+        oauth.register(
+            name="google",
+            client_id=app.config["OAUTH_GOOGLE_CLIENT_ID"],
+            client_secret=app.config["OAUTH_GOOGLE_CLIENT_SECRET"],
+            access_token_url="https://oauth2.googleapis.com/token",
+            authorize_url="https://accounts.google.com/o/oauth2/auth",
+            api_base_url="https://www.googleapis.com/oauth2/v1/",
+            client_kwargs={"scope": "openid email profile"},
+        )
+
+
+    if app.config.get("OAUTH_GITHUB_CLIENT_ID") and app.config.get("OAUTH_GITHUB_CLIENT_SECRET"):
+        oauth.register(
+            name="github",
+            client_id=app.config["OAUTH_GITHUB_CLIENT_ID"],
+            client_secret=app.config["OAUTH_GITHUB_CLIENT_SECRET"],
+            access_token_url="https://github.com/login/oauth/access_token",
+            authorize_url="https://github.com/login/oauth/authorize",
+            api_base_url="https://api.github.com/",
+            client_kwargs={"scope": "read:user user:email"},
+        )
+
+
+    if app.config.get("OAUTH_MICROSOFT_CLIENT_ID") and app.config.get("OAUTH_MICROSOFT_CLIENT_SECRET"):
+        oauth.register(
+            name="microsoft",
+            client_id=app.config["OAUTH_MICROSOFT_CLIENT_ID"],
+            client_secret=app.config["OAUTH_MICROSOFT_CLIENT_SECRET"],
+            access_token_url="https://login.microsoftonline.com/common/oauth2/v2.0/token",
+            authorize_url="https://login.microsoftonline.com/common/oauth2/v2.0/authorize",
+            api_base_url="https://graph.microsoft.com/v1.0/",
+            client_kwargs={"scope": "openid email profile"},
+        )
+
+
+@oidc_bp.route("/login/<provider>")
+def login(provider):
+    if not current_app.config.get("OAUTH_ENABLED", False):
+        abort_with_message(403, "OAuth is not enabled")
+
+
+    redirect_uri = request.args.get("redirect_uri", url_for("oidc.authorize", provider=provider, _external=True))
+    return oauth.create_client(provider).authorize_redirect(redirect_uri)
+
+
+@oidc_bp.route("/callback/<provider>")
+def authorize(provider):
+    if not current_app.config.get("OAUTH_ENABLED", False):
+        abort_with_message(403, "OAuth is not enabled")
+
+    client = oauth.create_client(provider)
+    token = client.authorize_access_token()
+
+    if provider == "google":
+        user_info = client.parse_id_token(token)
+    else:
+        user_info = client.get("user").json()
+
+    email = user_info.get("email")
+    if not email:
+        abort_with_message(400, "No email provided")
+
+    user = user_db.session.query(User).filter_by(email=email).first()
+    if not user:
+        # Enforce OIDC registration enable/disable
+        if not current_app.config.get("ALLOW_OIDC_REGISTRATION", True):
+            abort_with_message(403, "User registration is disabled")
+
+        # Determine the tree to use
+        if current_app.config["TREE"] == TREE_MULTI:
+            # In multi-tree, OIDC must know which tree to assign!
+            abort_with_message(422, "tree is required for OIDC registration in multi-tree mode")
+        tree_id = current_app.config["TREE"]
+        if not tree_exists(tree_id):
+            abort_with_message(422, "Tree does not exist")
+
+        try:
+            username = email.split("@", 1)[0]
+            dummy_password = uuid.uuid4().hex  # Satisfy non-empty password check
+            add_user(
+                name=username,
+                password=dummy_password,
+                email=email,
+                fullname=user_info.get("name", ""),
+                role=ROLE_USER,
+                tree=tree_id
+            )
+            user = user_db.session.query(User).filter_by(email=email).first()
+            if not user:
+                abort_with_message(500, "Failed to create user")
+        except ValueError as exc:
+            # Consistent error codes: 409 for conflict, 400 otherwise
+            msg = str(exc)
+            code = 409 if "exists" in msg.lower() else 400
+            abort_with_message(code, msg)
+
+    # Now continue as usual
+    tree_id = get_tree_id(str(user.id))
+    permissions = get_permissions(username=user.name, tree=tree_id)
+
+    access_token = create_access_token(
+        identity=str(user.id),
+        additional_claims={
+            "permissions": list(permissions),
+            "tree": tree_id
+        }
+    )
+    refresh_token = create_refresh_token(identity=str(user.id))
+
+    frontend_redirect = request.args.get("state") or current_app.config.get("FRONTEND_URL", "/")
+
+    response = {
+        "access_token": access_token,
+        "refresh_token": refresh_token,
+        "token_type": "Bearer",
+        "expires_in": current_app.config.get("JWT_ACCESS_TOKEN_EXPIRES", 900),
+        "user": {
+            "name": user.name,
+            "email": user.email,
+            "full_name": user.fullname,
+            "role": user.role,
+            "tree": tree_id
+        }
+    }
+
+    if request.headers.get("Accept") == "application/json":
+        return jsonify(response)
+
+    return redirect(f"{frontend_redirect}?access_token={access_token}&refresh_token={refresh_token}")
diff --git a/gramps_webapi/config.py b/gramps_webapi/config.py
index fd64a0ab..fc9b0c28 100644
--- a/gramps_webapi/config.py
+++ b/gramps_webapi/config.py
@@ -17,16 +17,21 @@
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 
+
 """Default configuration settings."""
 
+
 import datetime
 from pathlib import Path
 from typing import Dict
 
 
+
+
 class DefaultConfig(object):
     """Default configuration object."""
 
+
     PROPAGATE_EXCEPTIONS = True
     SEARCH_INDEX_DIR = "indexdir"  # deprecated!
     SEARCH_INDEX_DB_URI = ""
@@ -51,6 +56,12 @@ class DefaultConfig(object):
         "CACHE_THRESHOLD": 1000,
         "CACHE_DEFAULT_TIMEOUT": 0,
     }
+    PERSISTENT_CACHE_CONFIG = {
+        "CACHE_TYPE": "FileSystemCache",
+        "CACHE_DIR": str(Path.cwd() / "persistent_cache"),
+        "CACHE_THRESHOLD": 0,
+        "CACHE_DEFAULT_TIMEOUT": 0,
+    }
     POSTGRES_USER = None
     POSTGRES_PASSWORD = None
     POSTGRES_HOST = "localhost"
@@ -69,11 +80,25 @@ class DefaultConfig(object):
     LLM_MODEL = ""
     LLM_MAX_CONTEXT_LENGTH = 50000
     VECTOR_EMBEDDING_MODEL = ""
+    DISABLE_TELEMETRY = False
+
+
+    # OAuth configuration
+    OAUTH_GOOGLE_CLIENT_ID = ""
+    OAUTH_GOOGLE_CLIENT_SECRET = ""
+    OAUTH_GITHUB_CLIENT_ID = ""
+    OAUTH_GITHUB_CLIENT_SECRET = ""
+    OAUTH_MICROSOFT_CLIENT_ID = ""
+    OAUTH_MICROSOFT_CLIENT_SECRET = ""
+    OAUTH_ENABLED = False  # Master switch for OAuth functionality
+
+
 
 
 class DefaultConfigJWT(object):
     """Default configuration for JWT auth."""
 
+
     JWT_TOKEN_LOCATION = ["headers", "query_string"]
     JWT_ACCESS_TOKEN_EXPIRES = datetime.timedelta(minutes=15)
     JWT_REFRESH_TOKEN_EXPIRES = False
diff --git a/pyproject.toml b/pyproject.toml
index 38ad8801..1785e881 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -44,6 +44,7 @@ dependencies = [
     "gramps-ql>=0.4.0",
     "object-ql>=0.1.3",
     "sifts>=0.8.3",
+    "authlib",
 ]
 
 [project.optional-dependencies]
diff --git a/requirements-dev.txt b/requirements-dev.txt
index ea5aeadf..169f3b47 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -7,4 +7,4 @@ pydocstyle
 pre-commit
 celery[pytest]
 moto[s3]<5.0.0
-PyYAML
+PyYAML
\ No newline at end of file