Jelena Janković was born in Belgrade on 28 February 1985. Her elder brother Marko introduced her to tennis when she was about nine and a half, and she later trained at Nick Bollettieri's academy. In 2001 she won the Australian Open junior title and reached No. 1 in the junior rankings. She had turned professional in 2000 and began playing on the WTA Tour in 2001.
A right-hander with a two-handed backhand, she spent the following years climbing steadily, and in 2007 she won the Wimbledon mixed doubles with Jamie Murray, becoming the first Serbian woman to win a Grand Slam title. In 2008 she was runner-up at the Hopman Cup and reached her only major singles final at the US Open, losing to Serena Williams.
On 11 August 2008 she became world No. 1, and she finished 2008 at the top, the first player in WTA history to end a year at No. 1 without winning a Grand Slam singles title. Wikipedia gives two figures for her reign: 18 weeks in the summary and 17 consecutive weeks in the article, ending when Serena Williams overtook her on 2 February 2009. She reached the semifinals of the Australian Open and the French Open, and in 2012 she helped Serbia to its first Fed Cup final, which the Czech Republic won.
Over her career she won 15 singles titles, two doubles titles and one mixed doubles title, with a 644–370 singles record and more than 19 million US dollars in prize money. Her final seasons were cut short by injury: she had back surgery in October 2017 and missed the 2018 and 2019 seasons. In July 2022 she announced her retirement, saying her body no longer allowed her to play professionally.