diff --git a/config.example.py b/config.example.py
index e539040e..956ba963 100644
--- a/config.example.py
+++ b/config.example.py
@@ -9,6 +9,12 @@ class Config():
     TESTING = False
     # SSO auth enabled
     SSO_AUTH = False
+    # Authentication is done outside the app, use HTTP header to get the user uuid.
+    # If SSO_AUTH is set to True, this option is ignored and SSO auth is used.
+    HEADER_AUTH = True
+    # Name of HTTP header containing the UUID of authenticated user.
+    # Only used when HEADER_AUTH is set to True
+    AUTH_HEADER_NAME = 'X-Authenticated-User'
     # SSO LOGOUT
     LOGOUT_URL = "https://flowspec.example.com/Shibboleth.sso/Logout"
     # SQL Alchemy config
diff --git a/flowapp/__init__.py b/flowapp/__init__.py
index a29297a7..83433e06 100644
--- a/flowapp/__init__.py
+++ b/flowapp/__init__.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 import babel
 
-from flask import Flask, redirect, render_template, session, url_for
+from flask import Flask, redirect, render_template, session, url_for, request
 from flask_sso import SSO
 from flask_sqlalchemy import SQLAlchemy
 from flask_wtf.csrf import CSRFProtect
@@ -72,21 +72,9 @@ def login(user_info):
         else:
             user = db.session.query(models.User).filter_by(uuid=uuid).first()
             try:
-                session["user_uuid"] = user.uuid
-                session["user_email"] = user.uuid
-                session["user_name"] = user.name
-                session["user_id"] = user.id
-                session["user_roles"] = [role.name for role in user.role.all()]
-                session["user_orgs"] = ", ".join(
-                    org.name for org in user.organization.all()
-                )
-                session["user_role_ids"] = [role.id for role in user.role.all()]
-                session["user_org_ids"] = [org.id for org in user.organization.all()]
-                roles = [i > 1 for i in session["user_role_ids"]]
-                session["can_edit"] = True if all(roles) and roles else []
+                _register_user_to_session(uuid)
             except AttributeError:
-                return redirect("/")
-
+                pass
             return redirect("/")
 
     @app.route("/logout")
@@ -96,6 +84,19 @@ def logout():
         session.clear()
         return redirect(app.config.get("LOGOUT_URL"))
 
+    @app.route("/ext-login")
+    def ext_login():
+        header_name = app.config.get("AUTH_HEADER_NAME", 'X-Authenticated-User')
+        if header_name not in request.headers:
+            return render_template("errors/401.j2")
+        uuid = request.headers.get(header_name)
+        if uuid:
+            try:
+                _register_user_to_session(uuid)
+            except AttributeError:
+                return render_template("errors/401.j2")
+        return redirect("/")
+
     @app.route("/")
     @auth_required
     def index():
@@ -177,4 +178,20 @@ def format_datetime(value):
 
         return babel.dates.format_datetime(value, format)
 
+    def _register_user_to_session(uuid: str):
+        user = db.session.query(models.User).filter_by(uuid=uuid).first()
+        session["user_uuid"] = user.uuid
+        session["user_email"] = user.uuid
+        session["user_name"] = user.name
+        session["user_id"] = user.id
+        session["user_roles"] = [role.name for role in user.role.all()]
+        session["user_orgs"] = ", ".join(
+            org.name for org in user.organization.all()
+        )
+        session["user_role_ids"] = [role.id for role in user.role.all()]
+        session["user_org_ids"] = [org.id for org in user.organization.all()]
+        roles = [i > 1 for i in session["user_role_ids"]]
+        session["can_edit"] = True if all(roles) and roles else []
+
     return app
+
diff --git a/flowapp/auth.py b/flowapp/auth.py
index b4925d99..c4d942ff 100644
--- a/flowapp/auth.py
+++ b/flowapp/auth.py
@@ -14,7 +14,10 @@ def auth_required(f):
     @wraps(f)
     def decorated(*args, **kwargs):
         if not check_auth(get_user()):
-            return redirect("/login")
+            if current_app.config.get("SSO_AUTH"):
+                return redirect("/login")
+            elif current_app.config.get("HEADER_AUTH", False):
+                return redirect("/ext-login")
         return f(*args, **kwargs)
 
     return decorated
@@ -99,6 +102,12 @@ def check_auth(uuid):
         if uuid:
             exist = db.session.query(User).filter_by(uuid=uuid).first()
         return exist
+    elif current_app.config.get("HEADER_AUTH", False):
+        # External auth (for example apache)
+        header_name = current_app.config.get("AUTH_HEADER_NAME", 'X-Authenticated-User')
+        if header_name not in request.headers or not session.get("user_uuid"):
+            return False
+        return db.session.query(User).filter_by(uuid=request.headers.get(header_name))
     else:
         # Localhost login / no check
         session["user_email"] = current_app.config["LOCAL_USER_UUID"]
diff --git a/flowapp/templates/errors/401.j2 b/flowapp/templates/errors/401.j2
new file mode 100755
index 00000000..6fea372d
--- /dev/null
+++ b/flowapp/templates/errors/401.j2
@@ -0,0 +1,7 @@
+{% extends 'layouts/default.j2' %}
+{% block content %}
+  <h1>Could not log you in.</h1>
+  <p class="form-text">401: Unauthorized</p>
+  <p>Please log out and try logging in again.</p>
+  <p><a href="{{url_for('logout')}}">Log out</a></p>
+{% endblock %}
\ No newline at end of file