Marie de France (c.1200) was a French poet who had considerable influence over English writers. She spent most of her life at the English court. Some scholars believe she was the half-sister of Henry II of England, who was king during that time. She perfected the Breton lai, a type of narrative poem or song, and is probably responsible for its introduction in England. Many of Marie de France's lais had Celtic themes and included characters and storylines from the legends of King Arthur and his Knights of the Round Table.