Willemijntje den Ouden (1 January 1918 – 6 December 1997) was a competitive swimmer from the Netherlands, who held the 100-meter freestyle world record for nearly 23 years, from 1933 to 1956.

in 1931, at the age of 13, she became the Rotterdamsche Dames Zwemclub ("Rotterdam's Ladies Swimming Club") champion in her favorite discipline, 100m freestyle and broke the Dutch national record on that distance by 1.4 seconds with a time of 1:10.4.

[1] A year later, Den Ouden came in the international limelight when she participated at the 1932 Summer Olympics in Los Angeles and won two of the five contestable silver medals in swimming.

She did win the gold medal in the women's 4 × 100 m freestyle relay with her compatriots Tini Wagner, Rie Mastenbroek and Jopie Selbach.

Den Ouden herself fled to England, where in October 1943 she married Staffan Broms, son of a Swedish diplomat stationed in London.