Cornelis "Cees" Vervoorn (born 11 April 1960) is a retired swimmer from the Netherlands.

He competed at the 1976, 1980 and 1984 Summer Olympics in seven events; in 1980, he finished fourth, sixth and seventh in the 100 m and 200 m butterfly and 4 × 100 m medley relay, respectively.

After spending a year at the Southern Illinois University in the United States, he entered the Vrije Universiteit in Amsterdam (1980–1987).

In 1992 he defended a PhD on the "Neuro-endocrine aspects of exercise and training" at the Utrecht University.

Meanwhile, he was the national swimming coach at the 1984, 1988 and 1992 Olympics and the head of the Dutch Paralympics Team in 1996 and 2000 (he is not handicapped).