RIO DE JANEIRO - Australia's Mack Horton edged out defending champion Sun Yang of China to win Olympic men's 400m freestyle gold on Saturday.
He clocked 3 min 41.55sec, finishing 0.13sec ahead of two-time 400m free world champion Sun.
Italy's Gabriele Detti took bronze (3:43.49) at the Olympic Aquatics Stadium.
"It hasn't really sunk in yet," said Horton, who is also competing in the 1500m freestyle.
"I have a couple more races this week so I need to relax a little bit and focus on those but it's very exciting."
Sun, China's first male Olympic swimming champion, was hoping victory would put him back in the spotlight for the right reasons.
But even before the final, rivals hit out at the 24-year-old, who served a three-month ban in 2014 after testing positive for a banned stimulant.
Horton said: "I don't have time or respect for drug cheats."
Canada's Ryan Cochrane, who failed to qualify for the final, added: "I wish it was even across the board. For an athlete that's clean it's really frustrating. Once the Games are over, we'll all look back and wish this was handled better."