The 14-times grand slam winner only dropped one game in the women's final at Wimbledon, meaning she has only lost 17 in the entire tournament.
Wimbledon champion Williams, who is now on a 17-match winning streak, won the first set 6-0 and the second 6-1.
The 30-year-old had won the last seven matches she played against Sharapova, who will take home a silver medal.
Williams finished the match with two aces, asserting her utter dominance.
Her victory today matched her 6-1 6-0 win over another Russian, Vera Zvonareva, in the third round.
She jumped up and down with delight on clinching the Olympic title.
The USA player, 30, has lost just five games in the three Olympic finals she has won: 2000 Sydney doubles, 2008 Beijing doubles and 2012 London singles.
Sharapova, 25, was competing in her first Olympic Games and received enthusiastic support from the crowd.
In tomorrow's final they will meet Czech pair Lucie Hradecka and Andrea Hlavackova, where a victory would give them a third Olympic Doubles title together.