Juan Antonio Marín Casero (born 2 March 1975) is a former professional male tennis player from Costa Rica, who represented the Central American nation at the 2000 Summer Olympics in Sydney.

He originally played on tour under the Spanish flag, as he was born to a father from Murcia and a mother from Asturias, and lived in Spain since the age of 14.

[3] In October 1999, Marín reached his career-high singles ranking of world No.

2 Pete Sampras at the 1999 French Open, with the American eventually winning 6–7, 6–4, 7–5, 6–7, 6–4.

He never won a Grand Slam main draw match, despite appearing in 17.