Moonax (1991–2004) was an Irish-bred, English-trained Thoroughbred racehorse and sire. In 1994 Moonax became the first horse to win both the Classic St Leger and the Prix Royal-Oak and was named European Champion Stayer. He remains the only three-year-old to have been honoured in this way. He stayed in training until the age of six, winning only two more races, but finishing second in four Group One races.