Williams and Murray started their seasons at the tournament this year but Russian Sharapova will be making her first appearance at the event, which takes place at the Queensland Tennis Centre from December 31 to Jan. 6.
"Going into Australia after a long off season you always want to have the best possible matches," the 25-year-old, losing finalist at Melbourne Park this season, said.
"I tried to put Brisbane on the map last year but unfortunately couldn't make it out of injury... I have heard so many great things about it."
Williams beat Australian Open champion Victoria Azarenka at Flushing Meadows last week to win her 15th Grand Slam title and was looking forward to returning to Brisbane, despite injuring her ankle at the tournament in January.
"I love the tournament, it's great," she said. "It helps me prepare. I get a great tournament... tough field. I had so much fun this year but unfortunately it ended fast for me with a disaster of an injury."
Murray, who won his first Grand Slam title on Monday, was already confirmed to return to Brisbane to defend the title he won by beating Alexandr Dolgopolov.
The Australian Open, the first Grand Slam of the year, begins in Melbourne on January 14.