Klaas de Vries (born Terneuzen, 15 July 1944) is a Dutch composer. He is one of the founders of a music style that became known as the Rotterdam School.

Among the teachers of De Vries were Otto Ketting in the Netherlands and Milko Kelemen in Germany.

The scenic oratorio A King Riding, for which he received the 1988 Matthijs Vermeulen Award, is one of one of his best known works.

Klaas de Vries is a lecturer at the Conservatoire of Rotterdam. Among his many students are Thorkell Atlason, António Chagas Rosa, Oscar van Dillen, Andreas Kunstein, Sergio Luque, César de Oliveira, Joey Roukens, Edward Top, Jian-Hua Zhuang, Evrim Demirel.