diff --git a/changelog.d/13350.bugfix b/changelog.d/13350.bugfix
new file mode 100644
index 0000000000..46c496a6a0
--- /dev/null
+++ b/changelog.d/13350.bugfix
@@ -0,0 +1 @@
+Disable autocorrection and autocapitalisation on the username text field shown during registration when using SSO.
diff --git a/synapse/res/templates/sso_auth_account_details.html b/synapse/res/templates/sso_auth_account_details.html
index 1ba850369a..cf72df0a2a 100644
--- a/synapse/res/templates/sso_auth_account_details.html
+++ b/synapse/res/templates/sso_auth_account_details.html
@@ -138,7 +138,7 @@
         <div class="username_input" id="username_input">
           <label for="field-username">Username (required)</label>
           <div class="prefix">@</div>
-          <input type="text" name="username" id="field-username" value="{{ user_attributes.localpart }}" autofocus>
+          <input type="text" name="username" id="field-username" value="{{ user_attributes.localpart }}" autofocus autocorrect="off" autocapitalize="none">
           <div class="postfix">:{{ server_name }}</div>
         </div>
         <output for="username_input" id="field-username-output"></output>