William Kerr, first Earl of Lothian of a new creation (1605–1675) was a Scottish nobleman.
He was appointed one of the four commissioners of the treasury in 1642, was lieutenant-general of the Scots Army in Ireland, and was appointed privy councillor in the same year.
He entered Parliament in 1644 and joined Lord Argyll in expedition against Lord Montrose during the Wars of the Three Kingdoms in 1644. He was one of the commissioners sent to treat with the king at Holmby House in 1647.
He was appointed secretary of state in 1649 and was one of the commissioners sent by the Scottish Parliament to protest against proceeding to extremities against the king. he was a general of the Scottish forces in 1650. In 1662 he refused to take the abjuration oath.
The eldest son of Sir Robert Kerr, later 1st Earl of Ancram, he was born within St James's Palace in London and was educated at Cambridge University and at Paris. He accompanied George Villiers, 1st Duke of Buckingham to the Isle of Rhé in 1627 and served in the expedition against Spain in 1631.
He married Anne Kerr, 3rd Countess of Lothian in 1630 and was created Lord Kerr of Newbattle and Earl of Lothianin his own right in 1631. He signed the national covenant in 1638, and was Governor of Newcastle in the same year.