Johannes ("Jan") Marinus Plantaz (December 3, 1930 in Geldrop, Noord-Brabant – February 10, 1974 in Eindhoven, Noord-Brabant) was a road bicycle and track cyclist from the Netherlands, who represented his native country at the 1952 Summer Olympics in Helsinki, Finland.
There he was eliminated in the quarterfinals of the men's 4.000m team pursuit, alongside Adrie Voorting, Daan de Groot and Jules Maenen. In the men's individual road Plantaz ended up in 22nd place.