Williams posted an amazing 6-0, 6-1 victory over fifth-seeded Sara Errani in just 46 minutes after Sharapova, the No. 2 seed, out-battled the third-seeded Azarenka for a 6-1, 2-6, 6-4 victory that took 2 hours, 10 minutes.
Sharapova will be seeking her fifth major tournament title in Saturday's final. She's won each of the four events once, completing the career Grand Slam in last year's French Open.
Sharapova is 2-13 versus Williams -- including losses last year in the finals at the Olympics and WTA Championships and this year in title matches in Miami and Madrid. She has not beaten the American since 2004.
Williams currently holds two Grand Slam titles -- having won at Wimbledon and the U.S. Open last year -- but hasn't been in the French Open final since she won the tournament in 2002.
Williams extended her personal winning streak to 30 matches and improved to 6-0 versus Errani by taking the first nine games of the match. Errani managed a hold in the 10th game but Williams answered with a hold at love. Williams had six games -- two off Errani's serve on -- in which she didn't allow Errani a point.
Williams won 52 of the 68 points in the match, firing five aces and 40 winners against 12 unforced errors.
The day's first match was entirely different. After having her serve broken in the first game of the match, Sharapova dominated the rest of the first set. Azarenka -- ranked third in the world -- righted her game and didn't allow Sharapova a break opportunity in the second set.
There was a 30-minute rain delay before the third set and Sharapova seemed to use the time better, using a pair of breaks to get to 5-2. But, in a game indicative of the match, Sharapova had back-to-back double faults in losing an 18-point game in which she also had four match points.
Azarenka posted a quick hold but Sharapova answered with a hold at love, closing the match with her 12th ace of the match.