Herman "Flying Dutchman" Willemse (22 May 1934[1] – 7 July 2021[2]) was a Dutch long-distance and marathon swimmer.

In 1959, he switched to marathon swimming and became the second Dutchman to cross the English Channel, with a time of 12h49.

For three years after 1964, when the point system was introduced, he was ranked world number two, after Abo Heif.

[3][6][7] His clean sweep of the Around-the-Island Marathon Swim in 1960–1964 brought the organizers to a problem that spectators lost interest in the race.

[8] A school teacher by profession, Willemse was known for his academic approach to swimming.