Kirsty Coventry, who studies liberal arts at Auburn University in Alabama, walked a red carpet at Harare's airport on her arrival from Greece on Wednesday to the sound of African drums while thousands of her black compatriots danced and sang.
Mugabe -- who frequently makes headlines for his tough stance toward Zimbabwe's minority whites -- held an official welcome party for Coventry and presented her with $50,000 and a diplomatic passport.
Coventry became her country's first Olympic gold medallist in 24 years after winning the 200 metres backstroke in Athens. She also took silver in the 100 metres backstroke and a bronze in the 200 metres individual medley.
Coventry's medal haul in Athens has lifted spirits in Zimbabwe, mired in an economic and political crisis that many opponents blame on Mugabe's rule.
Zimbabwe's last Olympic gold medal was won by its women's hockey team in Moscow in 1980.
"She did us proud indeed. It is really in response to what she has done to us that we should have this welcome at home," Mugabe said, calling her a "golden girl".
Coventry said in interviews in Athens that she was overjoyed to be representing her country and did not believe that politics should interfere with sport.
Zimbabwe's political problems have intensified in recent years as Mugabe's government seized white-owned farms to give to landless blacks, an often violent programme it says addresses imbalances left from decades of British colonial rule.
The 80-year-old president, in power since independence in 1980 and one of Africa's veteran guerrilla freedom fighters, often attacks Zimbabwe's dwindling number of white residents as "kith and kin" of Zimbabwe's former rulers.
