Kirsten "Flipper" Flipkens (Dutch pronunciation: [ˈkɪrstə(ɱ) ˈflɪpkə(n)s]; born 10 January 1986) is a Belgian tennis coach and a former professional player. She reached a career-high ranking of world No. 13. Flipkens has won one singles title on the WTA Tour, winning the 2012 Tournoi de Québec, as well as seven doubles titles. She also won 13 singles titles and two doubles titles on the ITF Women's Circuit, and one singles title on the WTA Challenger Tour.

She had success as a junior, winning the girls' doubles title at the 2002 US Open and the singles titles at the 2003 Wimbledon Championships and the 2003 US Open. Her best Grand Slam performance as a senior was at the 2013 Wimbledon Championships, where she reached the semifinal. In the same year, she was crowned Sportswoman of the Year at the Belgian Sport Awards. In 2016, Flipkens entered her first Olympic Games in Rio de Janeiro and made it to the third round in singles. She is also the Belgian player who has played the most years in Fed Cup (16 years as of 2019). For this reason, she received the Fed Cup Commitment Award in 2016.

Flipkens was born on 10 January 1986 in Geel, Belgium as the only child of a car dealer and a housewife. She began playing tennis at four years old. Flipkens played tennis, football, volleyball and basketball before eventually deciding to pursue a career as a tennis player at the age of 12. She then went to the tennis academy in Wilrijk where she became friends with Kim Clijsters. At the age of 17, after winning Wimbledon and the US Open as a junior, she dropped out of school to continue her career as a professional tennis player. She speaks Dutch, English, French and German. One of her trademarks is her prescription glasses, which she needs to wear due to being near-sighted.

In 2001, Flipkens won the bronze medal at the European Youth Olympic Festival in Murcia, Spain.

In 2002, Flipkens and Elke Clijsters won the US Open girls' doubles title, beating Shadisha Robsinon and Tory Zawacki in the final with 6–1, 6–3.

In 2003, Flipkens won the Wimbledon Championships in girls' singles, beating Anna Chakvetadze 6–4, 3–6, 6–3 and the US Open in girls' singles, defeating Michaëlla Krajicek, 6–3, 7–5. Following her two wins in two major juniors events, Flipkens was selected to join the Belgium Fed Cup team for the 2003 Fed Cup's semifinal opposing the United States. She played her first Fed Cup match against then WTA No. 17, Meghann Shaughnessy and lost 7–6, 6–7, 7–9. She finished 2003 as world No. 1 of the junior rankings in both singles and doubles. At the end of the year, she was awarded Best Belgian Talent and named ITF Junior World Champion.

Flipkens played her first professional match on the ITF Women's Circuit in 2001 at the age of 15. Next year, she won her first ITF singles title at a $10k event in Pétange, when she defeated German qualifier Tanja Hirschauer, and two weeks later another $10k title in Koksijde. The following year, Flipkens made her debut at the WTA Tour, at the Diamonds Games in Antwerp, but finished her participation at the beginning of the tournament. 2004 was the first year when she attempted to qualify in Wimbledon into the main draw of a major. After a first-round loss at the Gaz de France Stars in September, Flipkens stated that she struggled with a congenital back injury during the second half of 2004. She was unable to play for several months.

She made her return at $50k event in Saint-Gaudens in May 2005, but lost in her first match. In late May, she made her debut in the qualifying of the French Open. Later, she also failed in qualifying for Wimbledon and the US Open. In 2006, Flipkens made big steps further, reaching the main draws at the French Open, Wimbledon and the US Open. At the French Open, she recorded her first Grand Slam match win, defeating qualifier Virginie Pichet, but lost in the next round to Flavia Pennetta. At the US Open, she got to the same stage of tournament, falling to eventual semifinalist Jelena Janković, while at Wimbledon, she lost in the first round. She also partnered with British No. 2, Andy Murray, in mixed doubles at Wimbledon.