The Scilly naval disaster of 1707 was the loss of four warships of a Royal Navy fleet off the Isles of Scilly in severe weather on 22 October 1707. One thousand, five hundred and fifty sailors aboard the wrecked vessels lost their lives, making the incident one of the worst maritime disasters in the history of the British Isles. The main cause of the disaster was the navigators' inability to accurately calculate their positions.