The 22-year-old, the only man to clock below 13 seconds this year, exploded out of the blocks to take a lead that was never threatened and crossed the line in 13.05 to win a title that was once a virtual preserve of Americans.
It was the slowest winning time in an Olympic final since Canada's Mark McKoy won gold in 13.12 in Barcelona in 1992 but that was never going to bother McLeod, who also won the world indoor 60 metres hurdles title earlier this year.
"I'm elated," McLeod told reporters. "The feeling is indescribable.
"Never in a million years would I have thought I would be an Olympic champion and a world champion in one year.
Cuban-born Orlando Ortega was second in 13.17 to take silver for Spain, while Frenchman Dimitri Bascou claimed bronze in 13.24 ahead of compatriot Pascal Martinot-Lagarde.
Nineteen of the 27 previous Olympic high hurdles champions had come from the United States but the event provided only disappointment for the Americans on Tuesday.
National champion Devon Allen was fifth and his team mate Ronnie Ash, who looked likely get amongst the medals until he lumbered into the final hurdle, was disqualified.
With the exception of the 1980 Moscow Games, which they boycotted, the United States had never previously failed to provide a medallist in the 120-year history of the event at the Olympics.
The hurdler said he had been inspired by the multiple champions that ushered in the golden era of Jamaican sprinting.
"You just feed off them, (Usain) Bolt and Shelly-Ann Fraser, you see them go out and represent their country and they have fun and they win," he said.
"They harvest medals and you just want to do the same thing. It's contagious, you just want to go out and experience it."
Ortega, who transferred his national allegiance from Cuba to Spain last year, gave his adopted country its first men's medal on the Olympic track since Spain last hosted the Games 24 years ago.
"I was just thinking 'come on. Go, go finish'," he said. "I see the (big screen) TV and see my second place. I cannot believe this moment."
He said he was "a hurdler, not a sprinter... for now" but had far more important things planned than deciding where his future in athletics lay.
"Now I'm going to eat as much ice cream and cake as I can," he said.