Five other contenders
Nationality: American, Age: 34, World ranking: 1, Grand Slam titles: 21
Despite injury concerns, Williams insists she's ready to win her sixth Australian Open title.
With main rivals like Victoria Azarenka looking formidable, the world No. 1 might not have it easy this time.
Nationality: Spaniard, Age: 22, World ranking: 3, Grand Slam titles: 0
Started 2015 at what was then her career-high of world No. 21, but stormed to third by year-end, making her first Grand Slam final at Wimbledon and winning her biggest title yet in Beijing.
Nationality: Polish, Age: 26, World ranking: 4, Grand Slam titles: 0
Finished strongly last year, when she won the biggest title of her career at the WTA Finals. Has began this season by retaining her title in Shenzhen.
Nationality: Russian, Age: 28, World ranking: 5, Grand Slam titles: 5
Injury-plagued and hasn't been on court much since Wimbledon last year, when she lost to Williams in the semi-finals. Withdrew from last week's Brisbane International after hurting her forearm in practice.
Nationality: Belarusian, Age: 26, World ranking: 16, Grand Slam titles: 2
Most likely contender to upset Williams' Grand Slam dominance. After an injury-plagued two years, Azarenka stormed her way to her second Brisbane International crown last week without dropping a set - her first title since she beat Williams in Cincinnati in 2013.
PHOTOS: AFP, REUTERS, ST FILE