diff --git a/users/models/domain.py b/users/models/domain.py
index c238025..40a3e22 100644
--- a/users/models/domain.py
+++ b/users/models/domain.py
@@ -59,13 +59,14 @@ class Domain(models.Model):
 
     @classmethod
     def get_remote_domain(cls, domain: str) -> "Domain":
-        return cls.objects.get_or_create(domain=domain, local=False)[0]
+        return cls.objects.get_or_create(domain=domain.lower(), local=False)[0]
 
     @classmethod
     def get_domain(cls, domain: str) -> Optional["Domain"]:
         try:
             return cls.objects.get(
-                models.Q(domain=domain) | models.Q(service_domain=domain)
+                models.Q(domain=domain.lower())
+                | models.Q(service_domain=domain.lower())
             )
         except cls.DoesNotExist:
             return None
diff --git a/users/models/identity.py b/users/models/identity.py
index cfa8c2c..7730c8f 100644
--- a/users/models/identity.py
+++ b/users/models/identity.py
@@ -153,6 +153,7 @@ class Identity(StatorModel):
         if username.startswith("@"):
             raise ValueError("Username must not start with @")
         username = username.lower()
+        domain = domain.lower()
         try:
             if local:
                 return cls.objects.get(username=username, domain_id=domain, local=True)
@@ -300,7 +301,7 @@ class Identity(StatorModel):
         Given a username@domain handle, returns a tuple of
         (actor uri, canonical handle) or None, None if it does not resolve.
         """
-        domain = handle.split("@")[1]
+        domain = handle.split("@")[1].lower()
         try:
             response = await SystemActor().signed_request(
                 method="get",
@@ -381,7 +382,7 @@ class Identity(StatorModel):
             )
             if webfinger_handle:
                 webfinger_username, webfinger_domain = webfinger_handle.split("@")
-                self.username = webfinger_username
+                self.username = webfinger_username.lower()
                 self.domain = await get_domain(webfinger_domain)
             else:
                 self.domain = await get_domain(actor_url_parts.hostname)