Petrus Johannes "Piet" Keizer (14 June 1943 – 10 February 2017) was a Dutch professional footballer who played as a left winger.
As part of the "Total Football" Ajax Amsterdam team of the 1960s and 1970s, Keizer was particularly notable during the successive managerial tenures of Rinus Michels and Stefan Kovacs (1965–1973).
He is widely considered one of the greatest players in Dutch football history.
Dutch writer Nico Scheepmaker once said: "Cruyff is the best, but Keizer is the better one".