Factbox on American Serena Williams, who will bid for her 22nd Grand Slam title against Angelique Kerber at the Australian Open on Saturday
Born in Michigan on September 26, 1981. (Age: 34)
Grand Slam career: 21 - Australian Open (2003, 2005, 2007, 2009, 2010, 2015); French Open (2002, 2013, 2015); Wimbledon (2002, 2003, 2009, 2010, 2012, 2015); U.S. Open (1999, 2002, 2008, 2012, 2013, 2014)
Making her name:
Learned to play the game with older sister Venus in Compton. Both were coached by their father Richard.
Turned professional in September 1995.
Won her first WTA Tour title in Paris in 1999, beating Amelie Mauresmo in the final.
Beats Martina Hingis in the U.S. Open final in 1999, becoming the first African-American woman to win a grand slam singles title since Althea Gibson in 1958.
Failed to make another grand slam final until 2001 when she lost in the U.S. Open final to older sister Venus.
Missed the 2002 Australian Open with injury then embarked on an incredible run that included winning five of the next six Grand Slams while losing in the semi-finals of the 2003 French open.
Career is affected by injury over the next four years, winning two Australian Open titles in 2005 and 2007 but failing to advance beyond the quarter-finals at the other three.
Wins US Open in 2008 to break the Grand Slam drought, having not won a major title since the 2007 Australian Open.
At the 2009 US Open, Williams was fined $175,000 and placed on a two-year probation for unsportsmanlike behaviour in her semi-final loss to Kim Clijsters.
Joins Billie-Jean King on all-time grand slam list in sixth with 12th Grand Slam title at 2010 Australian Open.
She missed the US Open in 2010 because of medical complications after cutting her foot on glass while celebrating her win at Wimbledon.
In 2011, she underwent surgery after a life-threatening blood clot was detected on her lung. She made the US Open final but lost to Australia's Sam Stosur.
Wins Wimbledon title in 2012 and follows that up with Olympic gold medal on the same grass courts just over a month later, beating top seed Victoria Azarenka in semi-finals and third seed Maria Sharapova in final.
Wins fourth US Open title in 2012, beating Azarenka in the final.
Crashes out to teenage compatriot Sloane Stephens in Australian Open quarter-final in 2013 but rebounds to claim her second Roland Garros title, one of 10 titles she wins that year as she reclaims top ranking.
Crashes out again early in 2014 Australian Open, but claims seven titles, including her sixth US Open, which is her third in succession, to join compatriots Chris Evert and Martina Navratilova on 18 Grand Slam titles.
Puts some poor early season form behind her to win her sixth Australian Open title and then goes on to win at Roland Garros and Wimbledon setting up an opportunity at US Open to clinch first calendar Grand Slam since Steffi Graf in 1988.
Loses in US Open semi-finals to Roberta Vinci and decides to take rest of the year off to recover from injuries and deal with loss of potential grand slam.
Finished 2015 with a 53-3 record and was named as Sports Illustrated magazine's Sportsperson of the Year, becoming just the third woman since its inception in 1956 to win the award.
Path to Final (Prefix denotes seeding)
1st round - bt Camila Giorgi (Italy) 6-4, 7-5
2nd round - bt Hsieh Su-wei (Taiwan) 6-1, 6-2
3rd round - bt Daria Kasatkina (Russia) 6-1, 6-1
4th round - bt Margarita Gasparyan (Russia) 6-2, 6-1
QF - bt 5-Maria Sharapova (Russia) 6-4, 6-1
SF - bt 4-Agniezska Radwanska (Poland) 6-0, 6-4
Australian Open finalist Angelique Kerber
Factbox on Germany's Angelique Kerber, who will bid for her first Grand Slam title against Serena Williams
Born in Bremen, Germany on January 18, 1988. (Age: 28)
Grand Slam career (best performances):
Australian Open - Final (2016); French Open - Quarter-final (2012); Wimbledon - Semi-final (2012); US Open - Semi-final (2011)
Began playing tennis aged three and grew up idolising Steffi Graf.
Turned professional in 2003 aged 15 and spent four years building the consistency needed to qualify for regular tour events
Made first main draw in 2006 at Hasselt in Belgium, losing to Serbia's Ana Ivanovic in the second round.
Cracked the top-100 for the first in May 2007 and made the first WTA quarter-final at 's-Hertogenbosch. Made her first grand slam main draw at Roland Garros, which she followed up at Wimbledon and the US Open, though she lost in the first round of each.
Played her first Australian Open main draw in 2008, reaching the second round before losing to Italy's Francesca Schiavone.
Makes her first WTA tour final in Bogota in 2010, beating top seeded Argentine Gisela Dulko in the semi-finals before losing to local Mariana Duque-Mario 6-4, 6-3. Enters top 50 for the first time in July.
Has a breakthrough in 2011 with her first Grand Slam semi-final appearance at the US Open, losing to eventual champion Sam Stosur of Australia.
Begins 2012 with two semi-finals in Auckland and Hobart before she beats Maria Sharapova, the top seed, in the quarter-finals in Paris, then beats second seeded Frenchwoman Marion Bartoli to clinch her first title.
Beats Caroline Wozniacki to clinch her second title in Copenhagen and also makes finals at Eastbourne and Cincinnatti.
Also advances to quarter-final at Roland Garros and Wimbledon semi-finals, where she loses to Agnieszka Radwanska. Goes on to lose in the quarter-finals of the London Olympics tournament to Victoria Azarenka.
Made the WTA Tour Finals for first time and finishes the year a career-high fifth.
Despite continuing to remain in the top-10 she endures a frustrating 2014, where she makes four finals and loses them all.
Crashes out in first round of 2015 Australian Open to Romania's Irina-Camelia Begu, though wins four titles on four different surfaces, becoming the first woman since Jelena Jankovic in 2007 to win WTA Tour titles on green clay, red clay, grass and hard courts.
Qualified for her third season-ending WTA Finals, beating Petra Kvitova in the round robin and needed to win just one set against Czech Lucie Safarova to advance to semi-finals but lost 6-4 6-3.
Makes the final of the 2016 Brisbane International before the season-opening grand slam, losing to Azarenka. Withdrew from the second round of the Sydney tournament with gastro-intestinal illness.
Almost repeats her first round exit of 2015 at Melbourne Park when she is forced to save a match-point against Japan's Misaki Doi, while she found herself 2-5 down in the second set against Azarenka in the last eight before recovering to reel off five successive games.
Path to Final (prefix denotes seeding):
1st round - bt Misaki Doi (Japan) 6-7(4), 7-6(6), 6-3
2nd round - bt Alexandra Dulgheru (Romania) 6-2, 6-4
3rd round - bt Madison Brengle (US) 6-1, 6-3
4th round - bt Annika Beck (Germany) 6-4, 6-0
QF - bt 14-Victoria Azarenka (Belarus) 6-3, 7-5
SF - bt Johanna Konta (Britain) 7-5, 6-2