diff --git a/keystoneauth1/adapter.py b/keystoneauth1/adapter.py
index a82b9bf9..4ae29448 100644
--- a/keystoneauth1/adapter.py
+++ b/keystoneauth1/adapter.py
@@ -45,13 +45,18 @@ class Adapter(object):
     :type logger: logging.Logger
     :param dict allow: Extra filters to pass when discovering API versions.
                        (optional)
+    :param dict additional_headers: Additional headers that should be attached
+                                    to every request passing through the
+                                    adapter. Headers of the same name specified
+                                    per request will take priority.
     """
 
     @positional()
     def __init__(self, session, service_type=None, service_name=None,
                  interface=None, region_name=None, endpoint_override=None,
                  version=None, auth=None, user_agent=None,
-                 connect_retries=None, logger=None, allow={}):
+                 connect_retries=None, logger=None, allow={},
+                 additional_headers=None):
         # NOTE(jamielennox): when adding new parameters to adapter please also
         # add them to the adapter call in httpclient.HTTPClient.__init__ as
         # well as to load_adapter_from_argparse below if the argument is
@@ -69,6 +74,7 @@ class Adapter(object):
         self.connect_retries = connect_retries
         self.logger = logger
         self.allow = allow
+        self.additional_headers = additional_headers or {}
 
     def _set_endpoint_filter_kwargs(self, kwargs):
         if self.service_type:
@@ -100,6 +106,9 @@ class Adapter(object):
         if self.allow:
             kwargs.setdefault('allow', self.allow)
 
+        for k, v in self.additional_headers.items():
+            kwargs.setdefault('headers', {}).setdefault(k, v)
+
         return self.session.request(url, method, **kwargs)
 
     def get_token(self, auth=None):
diff --git a/keystoneauth1/session.py b/keystoneauth1/session.py
index e9c739b1..ee7596f0 100644
--- a/keystoneauth1/session.py
+++ b/keystoneauth1/session.py
@@ -200,6 +200,10 @@ class Session(object):
                               can be followed by a request. Either an integer
                               for a specific count or True/False for
                               forever/never. (optional, default to 30)
+    :param dict additional_headers: Additional headers that should be attached
+                                    to every request passing through the
+                                    session. Headers of the same name specified
+                                    per request will take priority.
     """
 
     user_agent = None
@@ -211,7 +215,7 @@ class Session(object):
     @positional(2)
     def __init__(self, auth=None, session=None, original_ip=None, verify=True,
                  cert=None, timeout=None, user_agent=None,
-                 redirect=_DEFAULT_REDIRECT_LIMIT):
+                 redirect=_DEFAULT_REDIRECT_LIMIT, additional_headers=None):
 
         self.auth = auth
         self.session = _construct_session(session)
@@ -220,6 +224,7 @@ class Session(object):
         self.cert = cert
         self.timeout = None
         self.redirect = redirect
+        self.additional_headers = additional_headers or {}
 
         if timeout is not None:
             self.timeout = float(timeout)
@@ -501,6 +506,9 @@ class Session(object):
             headers['Content-Type'] = 'application/json'
             kwargs['data'] = self._json.encode(json)
 
+        for k, v in self.additional_headers.items():
+            headers.setdefault(k, v)
+
         kwargs.setdefault('verify', self.verify)
 
         if requests_auth:
diff --git a/keystoneauth1/tests/unit/test_session.py b/keystoneauth1/tests/unit/test_session.py
index 1ec7d26c..512abf08 100644
--- a/keystoneauth1/tests/unit/test_session.py
+++ b/keystoneauth1/tests/unit/test_session.py
@@ -930,6 +930,56 @@ class AdapterTest(utils.TestCase):
                           self.TEST_URL,
                           'GET')
 
+    def test_additional_headers(self):
+        session_key = uuid.uuid4().hex
+        session_val = uuid.uuid4().hex
+        adapter_key = uuid.uuid4().hex
+        adapter_val = uuid.uuid4().hex
+        request_key = uuid.uuid4().hex
+        request_val = uuid.uuid4().hex
+        text = uuid.uuid4().hex
+
+        url = 'http://keystone.test.com'
+        self.requests_mock.get(url, text=text)
+
+        sess = client_session.Session(
+            additional_headers={session_key: session_val})
+        adap = adapter.Adapter(session=sess,
+                               additional_headers={adapter_key: adapter_val})
+        resp = adap.get(url, headers={request_key: request_val})
+
+        request = self.requests_mock.last_request
+
+        self.assertEqual(resp.text, text)
+        self.assertEqual(session_val, request.headers[session_key])
+        self.assertEqual(adapter_val, request.headers[adapter_key])
+        self.assertEqual(request_val, request.headers[request_key])
+
+    def test_additional_headers_overrides(self):
+        header = uuid.uuid4().hex
+        session_val = uuid.uuid4().hex
+        adapter_val = uuid.uuid4().hex
+        request_val = uuid.uuid4().hex
+
+        url = 'http://keystone.test.com'
+        self.requests_mock.get(url)
+
+        sess = client_session.Session(additional_headers={header: session_val})
+        adap = adapter.Adapter(session=sess)
+
+        adap.get(url)
+        self.assertEqual(session_val,
+                         self.requests_mock.last_request.headers[header])
+
+        adap.additional_headers[header] = adapter_val
+        adap.get(url)
+        self.assertEqual(adapter_val,
+                         self.requests_mock.last_request.headers[header])
+
+        adap.get(url, headers={header: request_val})
+        self.assertEqual(request_val,
+                         self.requests_mock.last_request.headers[header])
+
 
 class TCPKeepAliveAdapterTest(utils.TestCase):
 
diff --git a/releasenotes/notes/additional-headers-f2d16f85f5abe942.yaml b/releasenotes/notes/additional-headers-f2d16f85f5abe942.yaml
new file mode 100644
index 00000000..f18fa31e
--- /dev/null
+++ b/releasenotes/notes/additional-headers-f2d16f85f5abe942.yaml
@@ -0,0 +1,10 @@
+---
+prelude: >
+    Allow specifying additional_headers to the session and the adapter to add
+    headers to all requests that pass through these objects.
+features:
+  - Add the ability to provide additional_headers to the session and adapter
+    object. This will allow clients particularly to provide additional ways to
+    identify their requests. It will also hopefully provide an intermediate way
+    to handle setting microversions until we support them directly with
+    keystoneauth.