diff --git a/changelog.d/4220.feature b/changelog.d/4220.feature
new file mode 100644
index 0000000000..e7a3e40483
--- /dev/null
+++ b/changelog.d/4220.feature
@@ -0,0 +1 @@
+Rename login type m.login.cas to m.login.sso
diff --git a/synapse/rest/client/v1/login.py b/synapse/rest/client/v1/login.py
index 0010699d31..f6b4a85e40 100644
--- a/synapse/rest/client/v1/login.py
+++ b/synapse/rest/client/v1/login.py
@@ -27,7 +27,7 @@ from twisted.web.client import PartialDownloadError
 
 from synapse.api.errors import Codes, LoginError, SynapseError
 from synapse.http.server import finish_request
-from synapse.http.servlet import parse_json_object_from_request
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.types import UserID
 from synapse.util.msisdn import phone_number_to_msisdn
 
@@ -83,6 +83,7 @@ class LoginRestServlet(ClientV1RestServlet):
     PATTERNS = client_path_patterns("/login$")
     SAML2_TYPE = "m.login.saml2"
     CAS_TYPE = "m.login.cas"
+    SSO_TYPE = "m.login.sso"
     TOKEN_TYPE = "m.login.token"
     JWT_TYPE = "m.login.jwt"
 
@@ -105,6 +106,10 @@ class LoginRestServlet(ClientV1RestServlet):
         if self.saml2_enabled:
             flows.append({"type": LoginRestServlet.SAML2_TYPE})
         if self.cas_enabled:
+            flows.append({"type": LoginRestServlet.SSO_TYPE})
+
+            # we advertise CAS for backwards compat, though MSC1721 renamed it
+            # to SSO.
             flows.append({"type": LoginRestServlet.CAS_TYPE})
 
             # While its valid for us to advertise this login type generally,
@@ -384,11 +389,11 @@ class SAML2RestServlet(ClientV1RestServlet):
         defer.returnValue((200, {"status": "not_authenticated"}))
 
 
-class CasRedirectServlet(ClientV1RestServlet):
-    PATTERNS = client_path_patterns("/login/cas/redirect", releases=())
+class CasRedirectServlet(RestServlet):
+    PATTERNS = client_path_patterns("/login/(cas|sso)/redirect")
 
     def __init__(self, hs):
-        super(CasRedirectServlet, self).__init__(hs)
+        super(CasRedirectServlet, self).__init__()
         self.cas_server_url = hs.config.cas_server_url.encode('ascii')
         self.cas_service_url = hs.config.cas_service_url.encode('ascii')
 
diff --git a/synapse/static/client/login/index.html b/synapse/static/client/login/index.html
index 96c8723cab..bcb6bc6bb7 100644
--- a/synapse/static/client/login/index.html
+++ b/synapse/static/client/login/index.html
@@ -12,35 +12,30 @@
         <h1>Log in with one of the following methods</h1>
 
         <span id="feedback" style="color: #f00"></span>
-        <br/>
-        <br/>
 
         <div id="loading">
             <img src="spinner.gif" />
         </div>
 
-        <div id="cas_flow" class="login_flow" style="display:none"
-                onclick="gotoCas(); return false;">
-            CAS Authentication: <button id="cas_button" style="margin: 10px">Log in</button>
+        <div id="sso_flow" class="login_flow" style="display:none">
+            Single-sign on:
+            <form id="sso_form" action="/_matrix/client/r0/login/sso/redirect" method="get">
+                <input id="sso_redirect_url" type="hidden" name="redirectUrl" value=""/>
+                <input type="submit" value="Log in"/>
+            </form>
         </div>
 
-        <br/>
+        <div id="password_flow" class="login_flow" style="display:none">
+            Password Authentication:
+            <form onsubmit="matrixLogin.password_login(); return false;">
+                <input id="user_id" size="32" type="text" placeholder="Matrix ID (e.g. bob)" autocapitalize="off" autocorrect="off" />
+                <br/>
+                <input id="password" size="32" type="password" placeholder="Password"/>
+                <br/>
 
-        <form id="password_form" class="login_flow" style="display:none"
-                onsubmit="matrixLogin.password_login(); return false;">
-            <div>
-                Password Authentication:<br/>
-
-                <div style="text-align: center">
-                    <input id="user_id" size="32" type="text" placeholder="Matrix ID (e.g. bob)" autocapitalize="off" autocorrect="off" />
-                    <br/>
-                    <input id="password" size="32" type="password" placeholder="Password"/>
-                    <br/>
-
-                    <button type="submit" style="margin: 10px">Log in</button>
-                </div>
-            </div>
-        </form>
+                <input type="submit" value="Log in"/>
+            </form>
+        </div>
 
         <div id="no_login_types" type="button" class="login_flow" style="display:none">
             Log in currently unavailable.
diff --git a/synapse/static/client/login/js/login.js b/synapse/static/client/login/js/login.js
index bfb7386035..3a958749a1 100644
--- a/synapse/static/client/login/js/login.js
+++ b/synapse/static/client/login/js/login.js
@@ -1,7 +1,8 @@
 window.matrixLogin = {
-    endpoint: location.origin + "/_matrix/client/api/v1/login",
+    endpoint: location.origin + "/_matrix/client/r0/login",
     serverAcceptsPassword: false,
-    serverAcceptsCas: false
+    serverAcceptsCas: false,
+    serverAcceptsSso: false,
 };
 
 var submitPassword = function(user, pwd) {
@@ -40,12 +41,6 @@ var errorFunc = function(err) {
     }
 };
 
-var gotoCas = function() {
-    var this_page = window.location.origin + window.location.pathname;
-    var redirect_url = matrixLogin.endpoint + "/cas/redirect?redirectUrl=" + encodeURIComponent(this_page);
-    window.location.replace(redirect_url);
-}
-
 var setFeedbackString = function(text) {
     $("#feedback").text(text);
 };
@@ -53,12 +48,18 @@ var setFeedbackString = function(text) {
 var show_login = function() {
     $("#loading").hide();
 
+    var this_page = window.location.origin + window.location.pathname;
+    $("#sso_redirect_url").val(encodeURIComponent(this_page));
+
     if (matrixLogin.serverAcceptsPassword) {
-        $("#password_form").show();
+        $("#password_flow").show();
     }
 
-    if (matrixLogin.serverAcceptsCas) {
-        $("#cas_flow").show();
+    if (matrixLogin.serverAcceptsSso) {
+        $("#sso_flow").show();
+    } else if (matrixLogin.serverAcceptsCas) {
+        $("#sso_form").attr("action", "/_matrix/client/r0/login/cas/redirect");
+        $("#sso_flow").show();
     }
 
     if (!matrixLogin.serverAcceptsPassword && !matrixLogin.serverAcceptsCas) {
@@ -67,8 +68,8 @@ var show_login = function() {
 };
 
 var show_spinner = function() {
-    $("#password_form").hide();
-    $("#cas_flow").hide();
+    $("#password_flow").hide();
+    $("#sso_flow").hide();
     $("#no_login_types").hide();
     $("#loading").show();
 };
@@ -84,7 +85,10 @@ var fetch_info = function(cb) {
                 matrixLogin.serverAcceptsCas = true;
                 console.log("Server accepts CAS");
             }
-
+            if ("m.login.sso" === flow.type) {
+                matrixLogin.serverAcceptsSso = true;
+                console.log("Server accepts SSO");
+            }
             if ("m.login.password" === flow.type) {
                 matrixLogin.serverAcceptsPassword = true;
                 console.log("Server accepts password");
diff --git a/synapse/static/client/login/style.css b/synapse/static/client/login/style.css
index 73da0b5117..1cce5ed950 100644
--- a/synapse/static/client/login/style.css
+++ b/synapse/static/client/login/style.css
@@ -19,30 +19,23 @@ a:hover   { color: #000; }
 a:active  { color: #000; }
 
 input {
-   width: 90%
-}
-
-textarea, input {
-   font-family: inherit;
-   font-size: inherit;
    margin: 5px;
 }
 
-.smallPrint {
-    color: #888;
-    font-size: 9pt ! important;
-    font-style: italic ! important;
+textbox, input[type="text"], input[type="password"] {
+   width: 90%;
 }
 
-.g-recaptcha div {
-    margin: auto;
+form {
+    text-align: center;
+    margin: 10px 0 0 0;
 }
 
 .login_flow {
+    width: 300px;
     text-align: left;
     padding: 10px;
     margin-bottom: 40px;
-    display: inline-block;
 
     -webkit-border-radius: 10px;
     -moz-border-radius: 10px;