Willem Hermansz. van Diest (c. 1600 in The Hague – c. 1678 in The Hague), was a Dutch Golden Age seascape painter.
He was the father of the painter Jeronymus van Diest and a follower of Jan van Goyen, Jan Porcellis and Simon de Vlieger.[1] In 1656 he helped set up the Confrerie Pictura.