An only child, she was born in Moscow, Soviet Union to Alla and Sergei Kournikov; her family later emigrated to the United States. Presently, she resides in Miami, Florida.

Kournikova's major-league tennis career has been curtailed for the past several years, and possibly ended, by serious back and spinal problems. She has had some success at the singles game, but her specialty has been doubles, where she has at times been the world's #1 doubles player. With Martina Hingis as her partner, she won Grand Slam titles in Australia in 1999 and 2002.

Kournikova's playing style fits the profile for a doubles player, and is complemented by her being taller than the average tennis player. On occasion, she has been compared to such players as Pam Shriver and Peter Fleming, with numerous doubles championships to their credit playing with shorter partners, such as Martina Navratilova and John McEnroe. With their skill and good looks, Kournikova and Hingis jestingly called themselves "The Spice Girls of Tennis".

At ages 13 and 14, Kournikova made headlines in international junior tennis, winning several tournaments including the 1995 Italian Open. She was 14 years old when she ended 1995 as Junior European Champion Under 18 and ITF Junior World Champion Under 18.

Kournikova debuted in professional tennis at age 14 in the Fed Cup for Russia, the youngest player ever to participate and win. At age 15, she reached the fourth round of the 1996 U.S. Open, only to be stopped by then-top ranked player, Steffi Graf.

Kournikova was a member of the Russian delegation to the 1996 Olympic Games in Atlanta, Georgia. In 1997, as a 16-year-old, she reached the semi-finals of Wimbledon, where she lost to the eventual champion, Martina Hingis by a score of 6-3, 6-2. 1998 was her breakthrough year, when she broke into the WTA's top 20 rankings for the first time and scored impressive victories over Martina Hingis, Lindsay Davenport, and Steffi Graf. Kournikova's two Grand Slam doubles titles came in 1999 and 2002, both at the Australian Open in the Women's Doubles event with partner Martina Hingis, with whom she played frequently starting in 1999.

Kournikova proved a successful doubles player on the professional circuit, winning 16 tournament doubles titles, including two Australian Opens and being a finalist in mixed doubles at the U.S. Open and at Wimbledon, and reaching #1 ranking in doubles in the Women's Tennis Association tour rankings. Her pro career doubles record was 200-71. However, her singles career plateaued after 1999. For the most part, she managed to retain her ranking between #10 and #15 (her career high singles ranking was #8), but her expected finals breakthrough failed to occur; she only reached four finals out of 130 singles tournaments, never in a Grand Slam event, and never won one. As a player, Kournikova was noted for her footspeed and aggressive baseline play; however, her flat, high-risk groundstrokes tended to produce high numbers of errors and her serve was sometimes unreliable in singles. Her singles record is 209-129.

Her final playing years were marred by a string of injuries, especially back injuries, which caused her ranking to erode gradually. Kournikova has not played on the WTA tour since 2003, but still plays exhibition matches for charitable causes.

In late 2004, she participated in three events organized by Elton John and by fellow tennis players Serena Williams and Andy Roddick. In January 2005, she played in a doubles charity event for the Indian Ocean tsunami with John McEnroe, Roddick, and Chris Evert.

Kournikova was also a member of the Newport Beachbreakers in the World Team Tennis (WTT) competition in July and November 2005, playing doubles only. In November 2005, she teamed up with Martina Hingis, playing against Lisa Raymond and Samantha Stosur in the WTT finals for charity.

In a feature for ELLE magazine's July 2005 issue, Kournikova stated that if she were 100% fit, she would like to come back and compete again.

Most of Kournikova's fame has come from the publicity surrounding her personal life as well as numerous modeling shoots. During her debut at the 1996 U.S. Open at the age of 15, Kournikova's physical beauty was noticed by the world and soon pictures of her appeared in numerous magazines all over the planet.

Kournikova's marital status has been an issue on several occasions. There were conflicting rumors about whether or not she was engaged to hockey player Pavel Bure. There were reports that she married NHL hockey star Sergei Fedorov in 2001. Kournikova's representatives have denied this, but Fedorov stated in 2003 that the couple had married and since divorced. Kournikova currently has a relationship with pop star Enrique Iglesias (in whose video, "Escape", she appeared), and rumors that the couple had secretly married appeared in 2003 and again in 2005. Kournikova herself has consistently refused to directly confirm or deny rumors about the status of her personal relationships.

In 2000, Kournikova became the new face for Berlei's shock absorber sports bras range, and appeared in the highly successful "only the ball should bounce" bill board campaign. Photographs of her scantily-clad form have appeared in various men's magazines, including more than one much-publicized Sports Illustrated Swimsuit Issues (2004 – 2005), where she posed in bikinis and swimsuits, and in other popular men's publications such as FHM and Maxim. She has not posed topless or nude for any publications.

Kournikova was named one of People's 50 Most Beautiful People in 1998, 2000, 2002, and 2003 and was voted "hottest female athlete" and "hottest couple" (with Iglesias) on ESPN.com. In 2002 she also placed first in FHM's UK and US "sexiest women" polls, being voted the "sexiest woman in the world".

By contrast, ESPN — citing the degree of hype as compared to actual accomplishments as a singles player — ranked Kournikova 18th in its "25 Biggest Sports Flops of the Past 25 Years".

Kournikova had a small role (as a motel manager) in the 2000 film Me, Myself and Irene, starring Jim Carrey.