Herstmonceux Castle is a brick-built castle, dating from the 15th century, near Herstmonceux, East Sussex, England. It is one of the oldest significant brick buildings still standing in England. The castle was renowned for being one of the first buildings to use that material in England, and was built using bricks taken from the local clay, by builders from Flanders. It dates from 1441. Construction began under the then-owner, Sir Roger Fiennes, and was continued after his death in 1449 by his son, Lord Dacre. The castle has been owned by Queen's University at Kingston, a Canadian university, since 1993.

Herstmonceux is a village and civil parish in the Wealden District of East Sussex, England, which includes Herstmonceux Castle.