Simon Thelwall or Theloal (1525/26–1586), of , Llanynys, Denbighshire, was a Welsh politician. He was a Member (MP) of the Parliament of England for Denbigh Boroughs March 1553, October 1553, 1559 and 1571, and for Denbighshire in 1563. He married Margaret Griffith, daughter of William Griffith.