Cung Le used one "lucky" strike to cut short the script at UFC on Fuel 6 at the Cotai Arena in Macau.
The 40-year-old who has split his time between movies and MMA crumpled former middleweight champ Rich Franklin midway through the first round of the UFC's first stop in China.
"That's the biggest fight of my life," Le said on Fuel TV after the fight. "I couldn't ask for anything more. I am grateful. I don't know what to say. Lucky punch."
Franklin followed up a kick that caught Le in the quad and with a punch when Le unleashed the right hand that landed on Franklin's jaw.
"I came in and waited for him to punch and caught him with an overhand right," Le said.
Franklin appeared to be out before he hit the ground. He was tended to immediately as he lay on the mat, but righted himself as Cung was declared the winner.
Le, who has been a fast starter in his previous fights, was more measured in the first round against Franklin, who had the reach advantage. That changed quickly as Le used one punch for the first knockout on the card and one of the best in UFC this year.
Le, who concentrated on kickboxing early in his career, improved to 2-1 in UFC and 9-2 overall in MMA. Frankin's overall record fell to 29-8-0 with one no decision.
Thiago Silva earned the only submission of the night as he applied an arm triangle choke that forced Stanislav Nedkov to tap out in the third round of their light heavyweight bout. Up until the third round, Nedkov had been aggressor as he exchanged strikes with Silva, who appeared to be stunned in the second round.
Welterweight Dong Hyun Kim easily handled Paulo Thiago, a Brazilian fighter who was thought to have an upper hand on the ground. Kim, however, dominated the ground, nearly completing submissions at the end of each of the first two rounds before he earning the unanimous decision.
All the other fights on the main card also went to decision as Tiequan Zhang defeated Jon Tuck (unanimous), Takeya Mizugaki beat Jeff Hougland (unanimous) and Takanori Gomi edged Mac Danzig (split).