Sharapova won the first set but Williams settled into a groove and went on to a 4-6, 6-3, 6-0 victory.
Williams served up six aces and saved half of her nine break points compared to an 0-for-7 mark for Sharapova.
Sharapova, ranked second in the world, came into the match with a 2-11 record against Williams.
Beyonce flaunts bikini body, Blue Ivy in vacation pics
Couple mistakenly served bag of cash at McDonald's drive-thru