Marcel Reinier Wouda (born 23 January 1972 in Tilburg, Noord-Brabant) is a former Dutch competitive swimmer who became Netherlands' first world swimming champion when he won the world title in the 200m individual medley at the 1998 FINA World Championships in Perth, Australia. He is the coach of Olympic champions Maarten van der Weijden and Hinkelien Schreuder at the Nationaal Zweminstituut Eindhoven as well as open water swimmers Linsy Heister, Maaike Waaijer, Ferry Weertman, Job Kienhuis, Robert Lijesen, Allen Lindenberg, Hinkelien Schreuder, Bastiaan Tamminga, Arjen van der Meulen, Wendy van der Zanden, Tom Vangeneugden, Joeri Verlinden, and Maaike Waaijer.
Wouda grew up in Uden, where he joined the 'De Zeester' swimming club at a very young age. His trainers were Martien Swinkels and Rob Kennis, who brought him to the top of Dutch swimming. Wouda made his Olympic debut at the 1992 Olympics, where he was the sole male in the Dutch squad of eight females. He finished 22nd in the 200m individual medley and 19th in the 400m individual medley.
Afterwards he moved to the United States, where he joined University of Michigan in Ann Arbor, Michigan under the guidance of coach Jon Urbanchek, alongside swimmers like Eric Namesnik, Gustavo Borges, and Tom Dolan. At the 1993 European Aquatics Championships, he won the bronze medal in the 400m individual medley. He won the NCAA Championships in the 500 yard and 1650 yard freestyle and an NCAA team title in 1995.
Wouda moved back to the Netherlands, where coach Jacco Verhaeren coached him at the 1996 Olympics. There he finished in 4th place in the 200m individual medley, 5th place in the 400m individual medley, and 7th place in 4 × 200metre freestyle relay. At the 1998 FINA World Championships in Perth, Australia, Wouda became world champion in the 200m individual medley and won two silver medals in the 400m individual medley and the 4 x 200m freestyle relay. After the 2000 Olympics, a journalist from Dutch daily NRC Handelsblad, Mark Hoogstad, wrote a book describing the resurrection of Dutch swimming at the hand of Wouda's career.
Wouda was the head coach of Dutch junior swimming for two years, before being named assistant coach of Verhaeren in Eindhoven, in October 2006. He guided Maarten van der Weijden to his world title in the 2008 FINA World Open Water Swimming Championships and the Olympic title in the Olympic 10K Marathon Swim. He is also the coach of Hinkelien Schreuder who was part of the Dutch winning women's 4 × 100m freestyle relay at the 2008 Beijing Olympics.