Johannes Martinus ("Jan") Siemerink (born 14 April 1970) is a retired tennis player from the Netherlands.

The former Dutch Davis Cup captain reached a career-high ATP ranking of 14.

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).

Siemerink's best performance at a Grand Slam event came at Wimbledon in 1998, where he reached the quarterfinals by defeating Ctislav Doseděl, David Prinosil, Jonas Björkman and Magnus Larsson, before being knocked-out by Goran Ivanišević in three tie-breaks.

After his playing career Siemerink was captain of the Dutch Davis Cup team from 2006 until 2016.