Williams, who will be seeking her 15th Grand Slam title when the final is played Saturday night, rolled to a 6-1, 6-2 semifinal victory over Sara Errani.
Williams has lost only 19 games through her six matches at this year's tournament. She is currently on one of the best runs of her spectacular career, having lost only one match during her last four tournaments while winning at Wimbledon, the Olympics and Stanford, Calif.
Azarenka reached the championship match by defeating Maria Sharapova 3-6, 6-2, 6-4. Sharapova defeated Williams in the finals of this year's French Open to complete a career Grand Slam.
Sharapova served eight aces, but also had 10 double faults and suffered five service breaks. She committed 42 unforced errors to just 19 for Azarenka.
It will be only the second title match appearance for Azarenka in a Grand Slam event, the other occasion coming this year when she won the Australian Open.
Azarenka and Williams have met 10 times in their career and Williams has won nine of those matches.