Marcel Keizer (born 15 January 1969) is a Dutch football coach and former player and currently coach of Sporting CP.
He was technical coach of Eerste Divisie side FC Emmen. He was also the coach of Telstar for two seasons and took the reins at SC Cambuur in February 2016. In June 2016, he left Cambuur and became coach of Jong Ajax.
On 17 June 2017, Keizer became the new coach of Ajax on a two-year contract, after managing the youth side in the previous season, thus replacing the Borussia Dortmund-bound Peter Bosz. After 17 games Ajax was second in the Eredivisie ranking with five points behind the leader PSV. Keizer obtained 38 points from 17 games in the Eredivie. 51 goals were scored with 16 goals against. He was fired on 21 December 2017, after losing a cup match by penalties against FC Twente.