"Doing my victory lap, I literally kept screaming to everyone I know 'Are you kidding me?'," Centrowitz told reporters.
"There's nothing like (winning Olympic gold). It doesn't compare to anything else I've won in my life."
Matt Centrowitz wins
Image credit: Reuters
Centrowitz, who won a world championship bronze in 2011 and silver in 2013, ran the final lap in 50.62 seconds to take gold in a field stacked with African talent.
Second-placed Makhloufi, who also won silver in the 800m, became the second man after British great Sebastian Coe to finish on the podium for the men's 800m and 1,500m in the same Games. Coe won 1,500m and clinched silver over 800m in 1984.
Nick Willis, who took silver at the London Games, overcame several injury-plagued seasons to snatch a bronze medal in his fourth Olympic games.
"After 2008, I had three different surgeries, it took me four years to get back in to form," the 33-year-old Willis said, hinting that he may compete at the next Olympics in Tokyo.
"A lot of people write you off in your 30s. This is for all the 30-year olds."
Kiprop, who has run the fastest time of the year, faded in the final lap to finish sixth.