Britton, a 32-year-old mechanic and ex-Marine, says he raised his 18-inch chainsaw and met the lion head-on as it pounced.
"It batted me three or four times with its front paws, and as quick as I hit it with that saw, it just turned away," Britton told the Associated Press.
He wounded the animal with the blade and it ran off. Wildlife officials later killed the animal after they say it attacked a dog that had been brought in to track it. The mountain lion was emaciated and showing signs of starvation, officials said.
Britton credits his military training for helping him fight off the lion.
The Associated Press contributed to this report.