Kaia Kanepi (Estonian pronunciation: [ˈkɑi.ɑ ˈkɑnepi]; born 10 June 1985) is an Estonian inactive professional tennis player. She achieved her career-high ranking of world No. 15 on 20 August 2012 and has won four singles titles on the WTA Tour. She is currently competing in padel.

Described as a 'resident Grand Slam upset specialist' by The Guardian – with 19 wins over seeded players in the first week of Grand Slams; only two active players (Victoria Azarenka and Venus Williams) have more. She has also reached seven Grand Slam quarterfinals in all four championships (French Open in 2008 and 2012, Wimbledon in 2010 and 2013, the US Open in 2010 and 2017, and Australian Open 2022), becoming the first Estonian to achieve this and was the first Estonian to be ranked inside the world's top 15. Kanepi's numerous achievements have made her one of Estonia's most famous and successful professional tennis players in history. Kanepi reached her first final in 2006, becoming the first Estonian female player to do so, at the Gaz de France Stars where she lost to Kim Clijsters. She then won her first singles title at the Palermo Ladies Open in 2010, also becoming the first Estonian female player to win a title.

Kaia Kanepi was born in Haapsalu. Her father, Jaak (a real estate broker) and mother Anne (a homemaker) played tennis. They also have daughters Kadri, who won a tennis scholarship to study in the United States, and Karin, a dedicated horse rider. Kaia, who always watched her parents and sisters play, discovered her love for tennis at an early age. She started playing at the age of eight. Her family has always supported her desire to play professional tennis.

She reached world No. 1 in the International Tennis Federation (ITF) junior rankings before turning professional in 1999.

Kanepi represented Estonia in both the women's singles and women's doubles, partnering Maret Ani, at the 2004 Summer Olympics, losing in the first round of both events.

At the end of 2006, she reached her first WTA Tour final during the Gaz de France Stars tournament in Hasselt, Belgium. She came through three qualification rounds and beat Anne Kremer, Nathalie Dechy, Eleni Daniilidou, Francesca Schiavone, and Michaëlla Krajicek to eventually play the final against Kim Clijsters, to whom she lost in three sets.

At the 2007 Australian Open, Kanepi struggled, but defeated 28th-seeded Flavia Pennetta before losing to Alicia Molik in the second round. In Indian Wells, she defeated wildcard Kristina Brandi in the first round, but lost in the second round to 14th seed and eventual champion, Daniela Hantuchová. At the 2007 Sony Ericsson Open in Key Biscayne, Florida, she stunned Patty Schnyder in the second round, before losing to qualifier Vera Dushevina in the next round. In late July 2007, Kanepi reached the semifinals of the Gastein Ladies tournament in Austria, where she fell to Francesca Schiavone. This was her third career semifinal and first of the year. Afterwards, she made her top-40 debut at world No. 40.

After losing in the first round of Australian Open, Kanepi performed better in the next Grand Slam. At the French Open, Kanepi defeated sixth seed Anna Chakvetadze in the second round. She then defeated 29th-seeded Anabel Medina Garrigues for a place in the fourth round. Outplaying unseeded Petra Kvitová she reached the quarterfinals, where she was defeated by fourth seed Svetlana Kuznetsova in straight sets. Nonetheless, Kanepi made history by becoming the first Estonian female tennis player to reach a major quarterfinal.