Sir Blunderbrain is a brave Fraggle who appeared in a legend told in the Fraggle Rock episode "The Terrible Tunnel".

According to the Storyteller Fraggle, Sir Blunderbrain ventured into the Terrible Tunnel to release the Fraggles that had been captured by the tunnel, but "never came home again." He somewhat resembles Wembley, except with more hair on his chin and less on his head.