Stosur was born in Brisbane, Queensland, the daughter of Tony and Diane, and has two brothers, Dominic and Daniel. She is of Polish descent by way of a grandfather. When she was six the family house and business on the Gold Coast was destroyed by a flood, and the family decided to move to Adelaide. There she started playing tennis, when she was given a racket for Christmas at the age of eight. While her parents worked long hours at the cafe they had started, Stosur played at local courts with older brother Daniel, who later encouraged their parents to take her to tennis lessons. Stosur attended Helensvale State High School on the Northern Gold Coast. She went away on her first overseas trip at the age of 13, competing in the World Youth Cup in Jakarta, Indonesia.
At 14 she joined the Queensland Academy of Sport (QAS) under Geoff Masters and in 2001, when she was 16, Stosur joined the Australian Institute of Sport tennis program.
Stosur first played professional tennis in 1999 on the ITF circuit. She debuted on the Women's Tennis Association tour in 2000, losing in the first qualifying round of the Australian Open. In 2001 she won four straight ITF titles. In 2002 she lost in the first round at the Gold Coast event.
In 2003 Stosur won her first WTA singles matches, reaching the third round of the Australian Open. She lost in the third round to No. 7 seed, Daniela Hantuchová. She also qualified for a WTA event in Memphis.
In 2004 Stosur reached the semifinals of the Gold Coast event, before falling to Ai Sugiyama. The next week she reached the second round of the WTA tournament in Hobart, then the second round of the Australian Open. She later qualified for WTA events in Acapulco, Indian Wells, Vienna and Birmingham. Stosur competed at the Athens Olympics, where she lost in the first round. She continued to play WTA qualifying events, qualifying for the Japan Open and Bali in the autumn of 2004. At the end of the 2004 season, Stosur reached the doubles final in Québec City, partnered with Els Callens from Belgium.
Stosur began her 2011 season by competing at the Brisbane International as the top seed. Stosur defeated Czech qualifier Lucie Hradecká in the first round in straight sets, 7–6(1), 6–1, after overcoming two breaks of serve and saving two set points in the first set. Stosur then fell in straight sets to fellow Australian, Jarmila Groth in the second round.
After this tournament, Stosur competed at the Medibank Sydney International as the fourth seed. She was drawn to a tough first round opponent in the in-form Yanina Wickmayer. She won 7–5 6–4, but lost in the second round to Svetlana Kuznetsova.
Stosur was seeded 5th at the 2011 Australian Open. In the first round she easily overcame American wildcard and world number 443 Lauren Davis, 6–1 6–1, and continued her form in the second round against Vera Dushevina 6–3 6–2 but ended up losing in the third round to 25th seed Petra Kvitová, 7–6(5), 6–3.
Stosur's ranking rose to number 5 despite her early loss at the Australian Open. Stosur then rose to a new career high No. 4 following a quarterfinal showing at the Dubai Duty Free Tennis Championships.
Stosur had a disappointing start to the first American leg of the year falling in the 3rd round of the Indian Wells tournament to Dinara Safina, 6(2)-7, 4–6. At Miami, Stosur was seeded 4th and received a bye to the second round. She won her second round match against Zheng Jie 6–2 6–1, and then won again in the third round to 30th seed Lucie Šafářová, 6–0, 7–6(1). This was Stosur's first victory against Šafářová after losing to her in their other three encounters. However, her run was ended in the fourth round by 16th seed and former No. 1 Maria Sharapova, who defeated her, 6–4, 6–1.
After Miami, Stosur played at Charleston where she failed to defend her title – falling in the third round to Elena Vesnina in 2 sets. This will be Stosur's crucial clay season as she has over two thousand ranking points to defend including her finalist points at last year's French Open.
At Stuttgart, Stosur had 320 ranking points to defend for being last year's finalist. At fifth seed, Stosur defeated Spaniard María José Martínez Sánchez in the first round. In the second round, Stosur won against Daniela Hantuchová and made it 5–1 in head to head. At the quarterfinals, Stosur took on world no. 3 Vera Zvonareva. This is their first time they faced each other since last year's final at Charleston. In the end, Stosur prevailed in three sets 2–3, 6–3, 7–6(3) to make it Stosur's first win against a top 10 player for the year as well as her first third set tiebreaker win and made it 6–1 against Zvonareva. Stosur lost to Germany's Julia Görges in the semifinals 4–6 6–3 5–7 and will lose 120 points in her rankings, but rose to world no. 6. However, Stosur did end up winning in the doubles at Stuttgart, partnering Germany's Sabine Lisicki and defeating the German team of Kristina Barrois and Jasmin Wöhr in the final 6–1, 7–6(5).
Stosur's next tournament was the 2011 Mutua Madrileña Madrid Open, where she was the fifth seed and was to defend 250 ranking points. In the first round, Stosur defeated Gisela Dulko 3–6, 6–2, 6–2. She followed that up with another win against Daniela Hantuchová with a 7–6(1), 7–5 tally, but she in the third round to Anastasia Pavlyuchenkova in straight sets, 6(4)-7, 3–6.
She then competed in her second Premier 5 tournament in Rome with no ranking to defend as she didn't take part last year due to injury and fatigue. As the sixth seed, Stosur had a bye in the first round. In the second round, Stosur defeated Iveta Benešová 6–1, 7–5. In the third round, Stosur defeated qualifier Polona Hercog 6–3, 6–4. In the quarterfinals, Stosur defeated second seed Francesca Schiavone 6–2, 6–4. Stosur also defeated fourth seed Li Na in the semifinals 7–6(6), 6–0. In her first tournament final since the 2010 French Open Stosur faced former world No. 1 Maria Sharapova. Both players had not dropped a set since coming into the tournament. In the final Stosur suffered a debilitating straight sets 2–6, 4–6 loss to the seventh seed Sharapova, this extended her head to head against the Russian player to 0 wins – 8 losses. It was her first encounter and subsequent loss on the clay court to Sharapova. However Stosur had cited a nauseating illness the morning before the final, which was also incidentally delayed due to rain.
An accomplished doubles player, Stosur in her early years developed a serve-and-volley style of play but as the years progressed, she started to feel more comfortable hitting on the baseline and coming to the net less often. Although she is known for being a doubles specialist and having great volleys and drop-shots while playing doubles, in her singles matches, Stosur has a tendency to miss-hit these shots. Her right-handed forehand ground-strokes, hit with heavy top-spin, are considered her best evidenced by her often choosing to hit inside-out forehands. She can hit forehand winners from any side of the court, and her motion when hitting her forehands makes it hard for her opponents to guess where she will hit it to. Because of this, many players attack her backhand side which was considered a weakness of her game, however in 2010, Stosur adopted Pat Rafter's signature backhand slice to add to her game and help her set up points. She has also improved on her two-handed backhand and has even generated winners on occasion. Stosur is also noted for her athleticism and after bouncing back from a career-threatening Lyme's Disease, she has became one of the fittest players on tour.
Due to its power, kick and variety, Stosur's serve is widely considered as one of the best on the women's tour. Her first serve, however erratic, reaches more than 118 mph (190 km/h) on a regular basis. Her second, a high bouncing kick serve, is highly rated as being the best second serve in the women's game by media and players alike, and was thought to play a key role in her French Open success in 2009 and 2010. One thing that Stosur has changed in her game, thanks to coach David Taylor is the fact that her serve has been less predictable with Stosur sometimes even using her kick serve as first serves. Her good serving motion has helped her overhead smashes and she rarely misses those shots.
Her favourite surface is hard court, although to date, her best Grand Slam singles results have occurred on the clay of the French Open. Stosur has also mentioned her least favourite surface is grass and this is mostly due to the fact that her biggest weapons (top-spin forehand & kick-serve) are not very effective on this surface. Her performances at Wimbledon have reflected this as she has only gone past the second round once on the lone grass-court Grand Slam event.
In her earlier years on the WTA tour, Stosur's real weakness was her inability to handle the pressure at major matches, and for not being good at closing out matches. In her first four WTA tour finals, she won the first set only to eventually lose the match. On her off-days, she is susceptible to hitting over 50 unforced errors. She has shown great improvement in these areas, and these weaknesses are seen less frequently in her matches now, as exemplified in her calm dispatch of the four-time Roland Garros champion and former World No. 1 Justine Henin, one time Roland Garros champion and the then-current World No. 1 Serena Williams and former World No. 1 Jelena Janković in the 4th round, quarter-final and semi-final at the 2010 Roland Garros. Despite this, her inability to handle pressure under major matches was evident in the final against Francesca Schiavone, losing in straight sets and hitting many errors despite being the clear favourite to take the title.
As of 2009, Stosur's clothing sponsor is Lacoste. Her racquet is Babolat's Pure Storm model, and she endorses Oakley eyewear, particularly the Enduring model.
