Cornelis Wilhelm "Kees" Jonker (29 March 1909 in Amsterdam – 2 February 1987 in Steinach am Brenner) was a sailor from the Netherlands, who represented his country at the 1936 Summer Olympics in Kiel. Jonker, as crew member on the Dutch 6 Metre "De Ruyter", took the 8th place with helmsman Joop Carp and fellow crew members Ansco Dokkum, Ernst Moltzer, and Herman Looman. During the 1948 Summer Olympics in Torbay, Jonker helmed the Dragon "Joy", with crew members Biem Dudok van Heel and Wim van Duyl, to an 8th place.