Magdalena Johanna Maria "Marleen" Veldhuis (born 29 June 1979) is a retired swimmer from the Netherlands.

Veldhuis had a daughter in June 2010, causing her to miss the 2010 European Aquatics Championships, and she returned to swimming for the 2011 and 2012 seasons.

After she decided to focus completely on swimming, Veldhuis made her international debut during the 2002 European Aquatics Championships in Berlin, at the relatively late age of 23, where she won a bronze medal in the 4×100 m freestyle as part of a team with Manon van Rooijen, Chantal Groot and Wilma van Hofwegen.

In April 2003 she joined Topzwemmen Amsterdam (TZA) to train as a full-time professional under the guidance of Fedor Hes.

At the end of the week there was a bronze medal in the 4×100 m medley relay alongside Stefanie Luiken, Madelon Baans and Chantal Groot.

In October 2004 she avenged her failed individual Olympic campaign by winning the gold medal in the 50 m freestyle at the 2004 FINA Short Course World Championships in Indianapolis by beating Libby Lenton from Australia and Therese Alshammar from Sweden.

In the 4×100 m freestyle relay she received a silver medal together with Chantal Groot, Inge Dekker and newcomer Ranomi Kromowidjojo.

Alongside Inge Dekker, Ranomi Kromowidjojo, and another young talent Femke Heemskerk, she won bronze in the 4×100 m freestyle relay.

[5] She also broke the 4×100 m freestyle relay world record, together with Inge Dekker, Ranomi Kromowidjojo and Femke Heemskerk, and won the gold medal.

[6] Veldhuis also won a bronze medal in 4×100 m medley alongside Hinkelien Schreuder, Jolijn van Valkengoed and Inge Dekker.

At the 2008 Summer Olympics she won the gold medal in the 4×100 m freestyle relay together with Inge Dekker, Ranomi Kromowidjojo and Femke Heemskerk, they swam just 0.14 seconds outside their own world record.

[7] At the 2009 World Aquatics Championships in Rome, Italy she won the gold medal in the 4×100 m freestyle alongside Inge Dekker, Ranomi Kromowidjojo and Femke Heemskerk.

In 2011 Veldhuis won a gold medal at the 2011 World Aquatics Championships as part of the 4 × 100 m freestyle relay alongside Inge Dekker, Ranomi Kromowidjojo and Femke Heemskerk in a time of 3:33.96.