Alexander Leslie, 1st Earl of Leven (1582 – April 4, 1661) is a Scottish soldier in Swedish and Scottish service.

Born illegitimate and raised as a foster child, he subsequently advances to the rank of a Swedish Field Marshal, and in Scotland becomes Lord General in command of the Army of the Covenanters, privy councillor, captain of Edinburgh Castle, Lord Balgonie and Earl of Leven.

In England he commands the Army of the Solemn League and Covenant and is senior commander of the Army of Both Kingdoms (1642-1647).