Serena weathered the storm after Henin sent the match into a deciding third set to wrap up victory after two hours and seven minutes and retain the title she won last year.
“It was a great final and it could have gone any way,” Williams said after receiving the Daphne Akhurst Memorial Cup from Margaret Court, who won a record 24 grand slam singles titles.
Both players were suffering from nerves at the start then battling exhaustion at the end but still managed to provide the packed Melbourne Park center court crowd with some exquisite shotmaking and intense drama in their first grand slam final meeting.
Williams, wearing a citrus-colored outfit, thumped down 12 aces and 32 winners while Henin provided a reminder of the form that earned her seven grand slam titles, including the 2004 Australian Open, with 28 winners of her own.
“It was definitely a tough match mentally and physically,” she told a news conference.
“I felt like we both were out there trying to kind of prove something. I think we both did at the end of the day.”
Despite the loss, it was a personal triumph for Henin, who only returned to the professional circuit this month after quitting the game in May 2008.
Williams won the last four games then sealed her win with a backhand deep into the court.
“I thought I just gotta man up, this is my chance, no matter what I’ve got one more set and I just gotta get through it and I did,” Williams told the Seven Network.
“I thought I was just giving it to her at that point… I literally said to myself I need to man up and keep playing better.”
The win gave Williams her 12th grand slam singles title and she joined her American idol Billie Jean King, who was watching from the Rod Laver Arena stands, in equal sixth place on the list of female grand slam singles champions.
Williams also became the first woman to win five Australian Open titles since the game turned professional in 1968 and the first to successfully defend her title since Jennifer Capriati won in 2001 and 2002.
She almost missed the championship after landing in hot water following her foul-mouthed attack on a lineswoman during her loss to Clijsters at last year’s U.S. Open.
She escaped a suspension after the Grand Slam Committee opted to fine her but remains on a two-year probation.
The championship ends on Sunday when Roger Federer faces Andy Murray in the men’s singles final.