Jelena Janković (Serbian: Јелена Јанковић, Serbian pronunciation: ; born February 28, 1985) is a former World No. 1 Serbian professional tennis player.

Janković learned her first tennis skills in Tennis Club 'Red Star'. As a nine-and-a-half year old she was introduced to tennis by her elder brother and fitness coach Marko. She was later trained at the Tennis Academy of Nick Bollettieri. As a junior she won the 2001 Australian Open. In 2001, she started to play on the WTA Tour; she reached the second round at her first tournament at the Indian Wells Masters.

In October 2003, Janković entered the top 100 at No. 90 for the first time after winning her first ITF title in Dubai. Three months later, Janković garnered her first top 10 win against Elena Dementieva 6–1, 6–4 in the first round of the 2004 Australian Open. In May, Janković won her first WTA title, a Tier V event, in Budapest, defeating Martina Suchá in the final 7–6, 6–3. Following her win in Budapest, she reached No. 51 in the world. Elsewhere in her 2004 season, she defeated top 20 players Nadia Petrova (twice), Vera Zvonareva, Patty Schnyder and Paola Suárez. Janković finished 2004 ranked No. 28 in the world.