diff --git a/etiquette/objects.py b/etiquette/objects.py
index 6941b48..36a4f50 100644
--- a/etiquette/objects.py
+++ b/etiquette/objects.py
@@ -1157,6 +1157,7 @@ class Tag(ObjectBase, GroupableMixin):
 
         self.group_getter = self.photodb.get_tag
         self.group_getter_many = self.photodb.get_tags_by_id
+        self._cached_synonyms = None
 
     def __eq__(self, other):
         return self.name == other or ObjectBase.__eq__(self, other)
@@ -1232,6 +1233,9 @@ class Tag(ObjectBase, GroupableMixin):
         }
         self.photodb.sql_insert(table='tag_synonyms', data=data)
 
+        if self._cached_synonyms is not None:
+            self._cached_synonyms.add(synname)
+
         if commit:
             self.photodb.log.debug('Committing - add synonym')
             self.photodb.commit()
@@ -1255,10 +1259,13 @@ class Tag(ObjectBase, GroupableMixin):
 
         # Migrate the old tag's synonyms to the new one
         # UPDATE is safe for this operation because there is no chance of duplicates.
+        my_synonyms = self.get_synonyms()
         data = {
             'mastername': (self.name, mastertag.name),
         }
         self.photodb.sql_update(table='tag_synonyms', pairs=data, where_key='mastername')
+        if mastertag._cached_synonyms is not None:
+            mastertag._cached_synonyms.update(my_synonyms)
 
         # Because these were two separate tags, perhaps in separate trees, it
         # is possible for a photo to have both at the moment.
@@ -1340,13 +1347,16 @@ class Tag(ObjectBase, GroupableMixin):
             self.photodb.commit()
 
     def get_synonyms(self):
+        if self._cached_synonyms is not None:
+            return self._cached_synonyms.copy()
+
         syn_rows = self.photodb.sql_select(
             'SELECT name FROM tag_synonyms WHERE mastername == ?',
             [self.name]
         )
-        syn_names = [row[0] for row in syn_rows]
-        syn_names.sort()
-        return syn_names
+        synonyms = set(row[0] for row in syn_rows)
+        self._cached_synonyms = synonyms.copy()
+        return synonyms
 
     @decorators.required_feature('tag.edit')
     # GroupableMixin.join_group already has @transaction.
@@ -1413,6 +1423,9 @@ class Tag(ObjectBase, GroupableMixin):
 
         self.photodb._cached_frozen_children = None
         self.photodb.sql_delete(table='tag_synonyms', pairs={'name': synname})
+        if self._cached_synonyms is not None:
+            self._cached_synonyms.remove(synname)
+
         if commit:
             self.photodb.log.debug('Committing - remove synonym')
             self.photodb.commit()