|Residence||Monte Carlo, Monaco|
|Born||14 April 1970|
|Height||1.82 m (6 ft 0 in)|
|Plays||Left-handed (one-handed backhand)|
|Career record||273–272 (ATP, Grand Prix and Grand Slam level, and Davis Cup)|
|Highest ranking||No. 14 (12 October 1998)|
|Grand Slam Singles results|
|Australian Open||4R (1991)|
|French Open||3R (1997)|
|US Open||4R (1998)|
|Olympic Games||1R (1992, 1996)|
|Career record||203–185 (ATP, Grand Prix and Grand Slam level, and Davis Cup)|
|Highest ranking||No. 16 (14 October 1996)|
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.
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 quarterfinals by defeating Ctislav Doseděl, David Prinosil, Jonas Björkman and Magnus Larsson before being knocked-out by Goran Ivanišević. Siemerink is also known for winning a fourth set tiebreak against compatriot Richard Krajicek from 6–0 down in the 1994 US Open, though Krajicek eventually won the match.
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 semifinals 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 totaled $4,347,693.
Singles: 12 (4 wins, 8 losses)
|Win||1.||Apr 1991||Singapore||Hard||Gilad Bloom||6–4, 6–3|
|Loss||1.||Oct 1991||Vienna, Austria||Carpet (i)||Michael Stich||4–6, 4–6, 4–6|
|Loss||2.||Feb 1993||Marseille, France||Carpet (i)||Marc Rosset||2–6, 6–7(1–7)|
|Loss||3.||Jul 1995||Amsterdam, Netherlands||Clay||Marcelo Ríos||4–6, 5–7, 4–6|
|Loss||4.||Aug 1995||Long Island, USA||Hard||Yevgeny Kafelnikov||6–7(0–7), 2–6|
|Loss||5.||Oct 1995||Basel, Switzerland||Hard (i)||Jim Courier||7–6(7–2), 6–7(5–7), 7–5, 2–6, 5–7|
|Win||2.||Jun 1996||Nottingham, UK||Grass||Sandon Stolle||6–3, 7–6(7–0)|
|Loss||6.||Aug 1996||New Haven, USA||Hard||Alex O'Brien||6–7(6–8), 4–6|
|Loss||7.||Oct 1996||Vienna, Austria||Carpet (i)||Boris Becker||4–6, 7–6(9–7), 2–6, 3–6|
|Loss||8.||Nov 1997||Stockholm, Sweden||Hard (i)||Jonas Björkman||6–3, 6–7(2–7), 2–6, 4–6|
|Win||3.||Mar 1998||Rotterdam, Netherlands||Carpet (i)||Thomas Johansson||7–6(7–2), 6–2|
|Win||4.||Sep 1998||Toulouse, France||Hard (i)||Greg Rusedski||6–4, 6–4|
Doubles: 18 (10–7)
|Loss||1.||Jun 1991||Rosmalen, Netherlands||Grass||Richard Krajicek|| Hendrik Jan Davids
|Win||1.||Jul 1991||Hilversum, Netherlands||Clay||Richard Krajicek|| Francisco Clavet
|Loss||2.||Oct 1991||Berlin, Germany||Carpet (i)||Daniel Vacek|| Petr Korda
|6–3, 5–7, 5–7|
|Win||2.||Mar 1993||Miami, USA||Hard||Richard Krajicek|| Patrick McEnroe
|6–7, 6–4, 7–6|
|Win||3.||Feb 1994||Marseille, France||Carpet (i)||Daniel Vacek|| Martin Damm
|6–7, 6–4, 6–1|
|Win||4.||Jul 1994||Hilversum, Netherlands||Clay||Daniel Orsanic|| David Adams
|Loss||3.||Jan 1995||Doha, Qatar||Hard||Andrei Olhovskiy|| Stefan Edberg
|Win||5.||Jun 1995||Rosmalen, Netherlands||Grass||Richard Krajicek|| Hendrik Jan Davids
|Loss||4.||Jul 1995||Stuttgart, Germany||Clay||Ellis Ferreira|| Tomás Carbonell
|6–3, 3–6, 3–6|
|Win||6.||Oct 1995||Vienna, Austria||Carpet (i)||Ellis Ferreira|| Todd Woodbridge
|Win||7.||Jan 1996||Sydney, Australia||Hard||Ellis Ferreira|| Patrick McEnroe
|5–7, 6–4, 6–1|
|Win||8.||Apr 1996||Monte Carlo, Monaco||Clay||Ellis Ferreira|| Jonas Björkman
|2–6, 6–3, 6–2|
|Loss||5.||Jan 1997||Sydney, Australia||Hard||Paul Haarhuis|| Luis Lobo
|4–6, 7–6, 3–6|
|Loss||6.||Mar 1998||Copenhagen, Denmark||Carpet (i)||Brett Steven|| Tom Kempers
|Win||9.||Jun 1998||Rosmalen, Netherlands||Grass||Guillaume Raoux|| Joshua Eagle
|Loss||7.||Oct 1998||Toulouse, France||Hard (i)||Paul Haarhuis|| Olivier Delaître
|Win||-||Jun 1999||Rosmalen, Netherlands||Grass||Leander Paes|| Ellis Ferreira
|Win||10.||May 2000||Orlando, USA||Clay||Leander Paes|| Justin Gimelstob
- "ABN-AMRO; Siemerink wins for home crowd". The New York Times. 9 March 1998.
- Fred Buddenberg (11 December 2006). "Siemerink coach Davis Cup-team". Trouw (in Dutch).
- "Haarhuis vervangt Siemerink na tien jaar als Davis Cup-captain". NU.nl (in Dutch). 16 December 2016.
- Luigi Gatto (10 February 2018). "Former ATP top-15 Jan Siemerink becomes Ajax' team manager". Tennis World.