diff --git a/app/models/tag_alias.rb b/app/models/tag_alias.rb
index 1afdb43ac..4070e61e0 100644
--- a/app/models/tag_alias.rb
+++ b/app/models/tag_alias.rb
@@ -1,5 +1,7 @@
 class TagAlias < TagRelationship
-  validates_uniqueness_of :antecedent_name, scope: :status, conditions: -> { active }
+  # Validate that the alias doesn't exist yet when it's created or when a BUR
+  # is requested, but not when a BUR is approved (to allow failed BURs to be reapproved)
+  validates_uniqueness_of :antecedent_name, scope: :status, conditions: -> { active }, on: %i[create update request]
   validate :absence_of_transitive_relation
 
   before_create :delete_conflicting_relationships
diff --git a/app/models/tag_relationship.rb b/app/models/tag_relationship.rb
index 2c7fecfe8..58dfd17e4 100644
--- a/app/models/tag_relationship.rb
+++ b/app/models/tag_relationship.rb
@@ -115,8 +115,21 @@ class TagRelationship < ApplicationRecord
     end
   end
 
+  # Create a new alias or implication, set it to active, and update the posts.
+  # This method is idempotent; if the alias or implication already exists, keep
+  # it and update the posts again.
+  #
+  # @param antecedent_name [String] the left-hand side of the alias or implication
+  # @param consequent_name [String] the right-hand side of the alias or implication
+  # @param approver [User] the user approving the alias or implication
+  # @param forum_topic [ForumTopic] the forum topic where the alias or implication was requested.
   def self.approve!(antecedent_name:, consequent_name:, approver:, forum_topic: nil)
-    tag_relationship = create!(creator: approver, approver: approver, antecedent_name: antecedent_name, consequent_name: consequent_name, forum_topic: forum_topic)
+    tag_relationship = find_or_create_by!(antecedent_name: antecedent_name, consequent_name: consequent_name, status: "active") do |relationship|
+      relationship.creator = approver
+      relationship.approver = approver
+      relationship.forum_topic = forum_topic
+    end
+
     tag_relationship.process!
   end
 
diff --git a/test/unit/bulk_update_request_test.rb b/test/unit/bulk_update_request_test.rb
index 0930e0876..c2f3ba57e 100644
--- a/test/unit/bulk_update_request_test.rb
+++ b/test/unit/bulk_update_request_test.rb
@@ -539,6 +539,42 @@ class BulkUpdateRequestTest < ActiveSupport::TestCase
       end
     end
 
+    context "when a bulk update request fails" do
+      should "allow it to be approved again" do
+        @post = create(:post, tag_string: "foo aaa")
+        @bur = create(:bulk_update_request, script: "alias foo -> bar")
+
+        TagAlias.any_instance.stubs(:process!).raises(RuntimeError.new("oh no"))
+        @bur.approve!(@admin)
+        assert_raises(RuntimeError) { perform_enqueued_jobs }
+
+        assert_equal("aaa foo", @post.reload.tag_string)
+
+        assert_equal("failed", @bur.reload.status)
+        assert_not_nil(@bur.forum_topic)
+        assert_equal(@admin, @bur.approver)
+
+        @ta = TagAlias.find_by!(antecedent_name: "foo", consequent_name: "bar")
+        assert_equal("active", @ta.status)
+        assert_equal(@admin, @ta.approver)
+        assert_equal(@bur.forum_topic, @ta.forum_topic)
+
+        TagAlias.any_instance.unstub(:process!)
+        @bur.approve!(@admin)
+        perform_enqueued_jobs
+
+        assert_equal("aaa bar", @post.reload.tag_string)
+
+        assert_equal("approved", @bur.reload.status)
+        assert_not_nil(@bur.forum_topic)
+        assert_equal(@admin, @bur.approver)
+
+        assert_equal("active", @ta.reload.status)
+        assert_equal(@admin, @ta.approver)
+        assert_equal(@bur.forum_topic, @ta.forum_topic)
+      end
+    end
+
     should "create a forum topic" do
       bur = create(:bulk_update_request, reason: "zzz", script: "create alias aaa -> bbb")