The result gave Red Bull driver Verstappen an unassailable 113-point lead in the championship, making him only the third driver after Michael Schumacher and Sebastian Vettel to clinch the title with four races to spare.
Ferrari's Leclerc crossed the line second in front of Red Bull's Sergio Perez, but he was hit with a penalty after squeezing Perez in the final chicane and being deemed to have gained an advantage by leaving the track.
Verstappen was only informed he had retained his title midway through the post-race TV interview, and even the driver himself was not sure if he had sealed the deal. "It's a crazy feeling of course as I didn't expect it when I crossed the line," said a surprised Verstappen. "Was it going to be half points?
I didn't know how many points I was going to get. I was happy with the race we had." The race got off to a chaotic start in heavy rain.