Fort William Augustus (also known as Grassy Island Fort, Fort Phillips) was a British fort built on Grassy Island off of Canso, Nova Scotia during the lead up to Father Rale's War (1720). In the wake of The Squirrel Affair and the British attack on Fort St. Louis (at present-day Guysborough), Cyprian Southack urged Governor Richard Philipps to build the fort. The Fort was named after Prince William, Duke of Cumberland, a son of George II of Great Britain.