In sailing, a brigantine or hermaphrodite brig is a vessel with two masts, only the forward of which is square rigged.

Originally the brigantine was a small ship carrying both oars and sails. It was a favorite of Mediterranean pirates and its name comes from the Italian word brigantino, meaning brigand, and applied by extension to his ship. By the 17th century the term meant a two-masted ship. In the late 17th century, the Royal Navy used the term brigantine to refer to small two-masted vessels designed to be rowed as well as sailed, rigged with square rigs on the foremast and fore-and-aft rigging on the mainmast.

By the first half of the 18th century the word had evolved to refer not to a ship type name, but rather to a particular type of rigging: square rigged on the foremast and fore-and-aft rigged on the mainmast. The word "brig" is an 18th century shortening of the word brigantine, which came to mean a vessel square-rigged on both masts. The early Oxford English Dictionary (with citations from 1720 to 1854) still defined brig as being either identical to a brigantine, or alternatively, a vessel of similar sail plan to a modern brig. By the middle of the 19th century modern meanings had more or less stabilised, although purists continue to debate the exact differences, or lack of them, between brig, brigantine and hermaphrodite brig in both English and American usage.