Jarkko Kalervo Nieminen (born 23 July 1981) is a Finnish former professional tennis player. His highest ranking of world No. 13, achieved in July 2006, is a Finnish record. He has won two ATP singles titles and five doubles titles in his career. His best performances in Grand Slam tournaments have been reaching the quarterfinals of the 2005 US Open, the 2006 Wimbledon Championships, and the 2008 Australian Open.
Statistically Finland's best player to date, Nieminen is also the first and so far only Finnish player to have won an ATP singles title and to have reached the quarterfinals of a Grand Slam singles event. He is also notable for winning the shortest recorded Masters Tour tennis match in Open Era history, defeating Bernard Tomic in just 28 minutes and 20 seconds in the first round of the 2014 Sony Open Tennis. He was ranked inside the Top 75 11 times in 14 years (2001 to 2014).
On 23 June 2015, he announced his retirement from professional tennis at the end of the season, playing 2015 Stockholm Open as his last event.
His wife, Anu Nieminen, is Finland's top-ranked badminton women's single player.
In April 2016, it was announced that Nieminen will compete in floorball in season 2016–2017 at Finnish Salibandyliiga representing SC Classic.
As a junior Nieminen reached as high as No. 9 in the world in 1999 (and No. 20 in doubles), and won the 1999 Jr US Open.
Defeated Kristian Pless of Denmark to win his first junior Grand Slam, the US Open.
Finished the year at No. 11 in the world junior rankings.
Made his Davis Cup debut against Italy, losing to Andrea Gaudenzi.
Won his first Davis Cup match, beating Mikael Tillström of Sweden in a dead-rubber.
Became the first Finn to reach an ATP final since Leo Palin in 1981, beating Pless, Younes El Aynaoui, defending champion Thomas Johansson and three-time winner Thomas Enqvist, before losing to Sjeng Schalken in five sets in Stockholm.
Posted a 38–12 Challenger record, winning four titles.
Finished the year in the top 100 for the first time.
Reached clay-court finals in Estoril and Mallorca, losing to David Nalbandian and Gastón Gaudio, respectively.
Became the first Finnish player to end the season in the top 50.
Reached his fourth career ATP final in Munich, losing to Roger Federer.
Advanced to the fourth round at the 2003 French Open, losing to Fernando González.
Achieved Finland's first Wimbledon seeding (30)