Jan Siemerink (born April 14, 1970 in Rijnsburg, Netherlands) is a former professional tennis player from the Netherlands.
As a junior player, Siemerink was the Dutch 18-under champion in 1988. He also won the doubles title at the 1988 Orange Bowl junior championship in Florida.
Siemerink turned professional in 1989. Over the course of his career he won four top-level singles titles (at Singapore in 1991, Nottingham in 1996, and at Rotterdam and Toulouse in 1998). He also won ten tour doubles titles, the most significant of which were the Miami Masters in 1993 and the Monte Carlo Masters in 1996.
Siemerink's best performance at a Grand Slam event came at Wimbledon in 1998, where he reached the quarter-finals before being knocked-out by Goran Ivanisevic.
Siemerink played for the Netherlands in the Davis Cup between 1991 and 2001, compiling a 17-10 record. He helped the Netherlands reach the World Group semi-finals in 2001.
Siemerink's career-high rankings were World No. 14 in singles (in 1998) and World No. 16 in doubles (in 1996). His career prize-money totalled US$4,347,693. He retired from the professional tour in 2002.