William Legge, 1st Earl of Dartmouth (14 October 1672 – 15 December 1750), was Lord Privy Seal from 1713 to 1714.

The only son of George Legge, 1st Baron Dartmouth, he was educated as a town-boy at Westminster School.

In 1702, he was appointed a member of the Board of Trade and Plantations, and eight years later he became Secretary of State for the Southern Department and joint keeper of the signet for Scotland.

He was also noted for discretion; foreign ambassadors complained that it would be easier to get information from a brick wall than from Dartmouth.

In his private life, his fondness for laughing at his own jokes led to his nickname "the Jester".