Daphne Helena Koster (born 13 March 1981) is a retired Dutch football player, who played as a defender for Ajax in the Vrouwen Eredivisie.

[3] A powerful centre back, she was the captain of both the Netherlands women's national football team and Ajax.

[12] In 2009, Koster was a mainstay of the Dutch national team, which reached the semi-finals of UEFA Women's Euro 2009 in Finland.

[14] In June 2013, national team coach Roger Reijners selected Koster for the Netherlands' squad for the UEFA Women's Euro 2013 in Sweden.

[16] She became administrative manager of women's football for Ajax, and is part of changing the culture in the club after the incident with Marc Overmars.