Sir Watkin Lewes (1740 – 13 July 1821) was a Welsh politician in England. Lewes was the second son of Reverend Watkin Lewes, of Pen-y-Benglog, Melinau, and Ann Williams, of Treamlod (Ambleston), Pembrokeshire. He was educated at Shrewsbury School and at Magdalene College, Cambridge, from which he graduated in 1763. He was elected alderman for the London ward of Lime Street and Sheriff of London in 1772, and was knighted in 1773. In 1780 he was elected Lord Mayor of London.