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 for 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.
Defeated Nick Lindahl in the first round of the Australian Open, before losing a tight five-set match to Florent Serra in the second round after having two match points in the fourth set. In the doubles competition, he reached the semifinals with partner Michael Kohlmann, losing to the top seeds Bob Bryan and Mike Bryan.
Nieminen reached a Masters quarterfinal for the first time since 2006 after beating no. 7 Juan Martín del Potro in the third round of the Monte-Carlo Masters. He also reached the third round in Indian Wells and Miami.
At Wimbledon, Nieminen, who had already announced his retirement at the end of the season, played Lleyton Hewitt in the first round, with Hewitt also stating his intention to retire before the 2016 event. Nieminen earned his first win over Hewitt in five gruelling sets. At the US Open, Nieminen faced Jo-Wilfried Tsonga in the first round, with Tsonga prevailing in straight sets despite Jarkko's best efforts. Afterwards, he confirmed that this was his last match at a grand slam.
Nieminen played his final ATP match on 20 October at the 2015 Stockholm Open, losing 6–3, 6–7, 4–6 to Nicolas Almagro. Jarkko had match points in the second-set tiebreaker but narrowly missed one and was very unlucky to lose the other. Fellow Scandinavian tennis player Robin Söderling was in attendance to pay tribute to Jarkko and the Finn was visibly moved as he gave his farewell speech. His final official match was against his old friend and rival Roger Federer at the Hartwall Arena, Helsinki on the ninth of November.