Varner defeated Valerii Andriitsev of Ukraine in the finals to join Jordan Burroughs as an American winner at these Games. Burroughs captured the 74-kilogram gold medal on Friday.
It is the first time since 1996 that the United States has won more than one wrestling gold medal at the Olympics.
Varner, twice the NCAA champion while competing at Iowa State, defeated former world championship bronze medalist Kurbain Kurbanov of Uzbekistan along the way Sunday, downed Khetag Pliev of Canada in the quarterfinals and took out George Gogshelidze of Georgia in the semifinals.
Gogshelidze wound up with one of the two bronze medals awarded in what was the final wrestling event of the Olympics. The other one went to Khetag Gazyumov of Azerbaijan.
In the other wrestling final held Sunday, Japan's Tatsuhiro Yonemitsu won the 66-kilogram class over Sushil Kumar of India. Akzhurek Tanatarov of Kazakhstan and Livan Lopez Azcuy of Cuba received bronze medals.
There were 18 events conducted in men's and women's freestyle wrestling and men's Greco-Roman wrestling during the Olympics and both Russia and Japan finished with four gold medals.