Red-hot favourite Unique Bella was easily beaten as Bar Of Gold got up on the line to land the Breeders' Cup Filly & Mare Sprint at Del Mar.
Unique Bella was bidding to become the first three-year-old to win the contest, but after setting a blistering early pace she was swamped by rivals on the home turn.
Ami's Mesa led entering the final furlong and looked to have the race sewn up, but Irad Ortiz got Bar Of Gold up on the line to secure the mare's first Graded victory for trainer John Kimmel.
When asked if he knew he had won in the photo-finish, Ortiz said: "I thought I had it, I thought I got my head in front.
Ortiz added: "She was absolutely flying, she got a beautiful trip.
"She's been working good and when I first rode her work at Saratoga I knew she was a special filly, she always tries for me."
Kimmel said: " She's been a special filly and has had some bad luck in Graded races, but we knew one day she would come up good in a Grade One or Grade Two some time.
"To see her do this puts a stamp on her quality."