The Prix du Moulin de Longchamp is a Group 1 flat horse race in France open to horses aged three years or older. It is run at Longchamp over a distance of 1,600 metres (about 1 mile), and it is scheduled to take place each year in September.

Northjet was an Irish-bred, French-trained Thoroughbred racehorse and sire. He showed useful form in his early career, winning five races in Italy including the Group Two Premio Melton before being transferred to race in France in 1980. In early 1981 he won the Prix du Muguet but was beaten in several races and appeared to be just below the highest class. Northjet established his reputation in the late summer of 1981 when he recorded a five length victory over a very strong field in the Prix Jacques Le Marois and then won the Prix du Moulin in course record time. He was generally recognised as the best older horse and the best miler to race in Europe that season. He was then retired to stud where he was a complete failure as a breeding stallion.