Penzance (pĕnzănsˈ) [key], town (1991 pop. 18,501), Cornwall, SW England, at the head of Mounts Bay. Penzance is a resort and a port for the Scilly Islands. It also has flour mills. Penzance Library houses a notable Cornish collection. The town was sacked by the Spanish in 1595 and until the 18th cent. was subject to raids by Mediterranean pirates. Gilbert and Sullivan's operetta, The Pirates of Penzance, depicts the raids. The scientist Humphry Davy was born there.