Sir Roger Williams (1539–1540 – 12 December 1595) was a Welsh soldier of fortune and military theorist, who served the Protestant cause, fighting against the Spanish in several theatres of war. Robert Dudley, 1st Earl of Leicester said that as a soldier he was "worth his weight in gold". He was later a close associate of Robert Devereux, 2nd Earl of Essex, and became a national hero because of his exploits fighting the Catholic League. He has been described as "an obstreperous, opinionated Welsh soldier" who was "Essex's devoted confederate and agent".