Arrogate overhauled 4-5 favorite California Chrome in the final 100 yards to win the $6 million Breeders' Cup Classic on Saturday.
It was California Chrome's first loss in seven starts this year; Arrogate won his fifth straight race.
California Chrome and Victor Espinoza led most of the 1 1/4-mile race, with Melatonin second and Arrogate and Mike Smith loping along in third place.
"I was cruising on the lead. He was doing it so easy, so comfortable," Espinoza said. "Maybe I should have opened it up a little bit early."
Around the final turn, Arrogate took up the chase, with Smith first whipping the 3-year-old colt left-handed and then right through the stretch as they gained on California Chrome, the 2014 Horse of the Year who won the Kentucky Derby and Preakness that year.
"I gave him a few reminders left-handed," Smith said. "Then I went back right to surprise him. When I did that, he gave me another jump. That is what got us on by."
Arrogate caught California Chrome to win by a half-length, giving Smith his third Cup victory of the weekend and record 25th of his career. Trainer Bob Baffert earned his record third consecutive Classic win.
"I was surprised I beat him," Baffert said. "I didn't think I could beat him going in."
Arrogate finished in 2:00.11 and paid $5.40, $2.80 and $2.60.
California Chrome returned $2 and $2.40. Keen Ice was another 10 3/4 lengths back in third and paid $5.80 to show.
"You saw two champions run," said Art Sherman, California Chrome's 79-year-old trainer. "What can I say? We got outrun on the fair. No excuses. He ran his eyeballs out."
Hoppertunity, also trained by Baffert, was fourth. Melatonin finished fifth, followed by Frosted, Effinex, War Story and Win the Space, who didn't finish.
Shaman Ghost was scratched.