Azarenka hadn't dropped a three-set match all season until Sunday, going 12-0 in matches that went the distance, including victories over defending U.S. Open champion Sam Stosur in the quarterfinals and 2006 champion Maria Sharapova in the semifinals.
As the third set started, Williams' mother, Oracene Price, told her from the stands, "Settle down."
When Williams double-faulted, slapped a bad backhand into the net and pushed a forehand long, Azarenka broke at love for a 4-3 edge, then followed that up by holding for 5-3.
Azarenka was two points away at 30-30 with Williams serving in the next game, but couldn't convert. And when Azarenka served for the victory at 5-4, she showed the jitters that probably are understandable given that this was only her second career Grand Slam final, 17 fewer than Williams.
Azarenka made three errors in that game, including a forehand into the net that let Williams break her to 5-all. Williams kept whatever excitement she might have felt contained, face straight as possible, while her older sister, seven-time major champion Venus, smiled and clapped in the stands.
That was during a key stretch in which Williams took 10 of 12 points to go ahead 6-5. She then broke again to win, dropping onto her back on the court when Azarenka sent a backhand long to end it.
Azarenka slumped in her changeover chair, a white towel covering her head, as Williams kept saying, "Oh, my God! Oh, my God! Oh, my God!" while scurrying over to share the joy with her mother and big sister.