William Lewis (1625–1661) was an English landowner and politician who sat in the House of Commons in 1660.
Lewis was the second son of Sir Edward Lewis, a courtier, and his wife Lady Anne Sackville, daughter of Robert Sackville, 2nd Earl of Dorset and widow of Sir Edward Seymour.
His father owned The Van, Glamorgan, and Edington Priory, Wiltshire, and died in 1630.
His mother sent her eldest sons abroad during the English Civil War to prevent their uncles, William Seymour, 2nd Duke of Somerset and Edward Sackville, 4th Earl of Dorset, from engaging them in the royalist cause and he travelled in France and Italy between 1642 and 1646.
Richmond then remarried Frances Stewart ("la Belle Stuart"), much to the displeasure of King Charles II of England, who had hoped to make her his mistress.