Kooyonga was an Irish champion Thoroughbred racehorse who raced from 1990 to 1992. After showing good form as a juvenile, she had a highly successful three-year-old campaign, winning the Group One Irish 1,000 Guineas and the Coronation Stakes and being named European Champion Three-Year-Old Filly at the Cartier Racing Awards. She stayed in training as a four-year-old and became the second filly (after Pebbles) to win the Eclipse Stakes.

Kooyonga was bred in Ireland by Sean Collins at the Ovidstown Stud, near Maynooth, County Kildare. Her sire, Persian Bold was a successful racehorse who won the Richmond Stakes in 1977. He went on to be a "good" stallion, getting important winners such as Falcon Flight (Prix Hocquart), Persian Heights (St James's Palace Stakes) and Bold Russian (Celebration Mile). Kooyonga's dam, Anjuli, was an unraced half sister of the 2000 Guineas winner Roland Gardens.

Kooyonga was trained throughout her career by Michael Kauntze at Ashbourne, County Meath and ridden in all but three of her races by Warren O'Connor. Her name was derived from that of a Golf Club in South Australia.

Kooyonga first appeared on a racecourse in August when she won a maiden race at Gowran Park by three lengths. Four weeks later she was moved up to Listed class and won the Silver Flash Stakes at Phoenix Park by a head from the odds-on favourite African Dance. In October, she returned to Phoenix Park for the Cartier Million, a valuable sales race, in which she finished second to Rinka Das. On her final start she successfully moved to Group Three class to record a four length win in the Leopardstown Stakes.

Kooyonga began her three-year-old season with a win in the Listed Leopardstown 1000 Guineas Trial and was then sent to England for the 1000 Guineas at Newmarket. Ridden by Lester Piggott, the filly was held up in the early stages, before finishing strongly to finish second, two lengths behind the odds-on favourite Shadayid.

The Vincent O'Brien trained Rua d'Oro , who Piggott chose to ride rather than Kooyonga, was made favourite for the Irish 1,000 Guineas with Kooyonga starting at 4/1. Kooyonga proved much too good for the opposition, winning by three lengths under Warren O'Connor to record her first Group One win. Following the race she was bought as prospective broodmare by the Japanese businessman Mitsuo Haga for a fee of $1,200,000. The Coronation Stakes at Royal Ascot featured a rematch between Kooyonga and Shadayid, who, since her Newmarket win, had finished third in the Oaks. O'Connor tracked the leaders on his filly before moving her past Gussy Marlowe to take the lead in the straight. Shadayid emerged to make a challenge, but Kooyonga ran on strongly to reverse the Newmarket form and win by three quarters of a length.

In September, Kooyonga was prepared for an Autumn campaign with a run in the Matron Stakes, then a Group Three race, which she won by a length from Blue Daisy. She was then sent back to Ascot for the Queen Elizabeth II Stakes, which attracted a strong field including Shadayid, Hector Protector, Selkirk and Second Set, who was made favourite after his win in the Sussex Stakes. Kooyonga moved into second place behind Shadayid in the straight and ran on strongly to overtake the English filly but was herself passed in the final furlong and beaten one and a half lengths by Selkirk.

On her final start of the season she was sent to Churchill Downs for the Breeders' Cup Mile, but failed to reproduce her best form, finishing thirteenth of the fourteen runners behind Opening Verse