Jean Théodore Delacour (26 September 1890 – 5 November 1985) was an American ornithologist of French origin. He was renowned for not only discovering but also rearing some of the rarest birds in the world. One of the birds he discovered was the Imperial Pheasant, later found to be a hybrid between the Vietnamese Pheasant and the Silver Pheasant.
Delacour was born in Paris into a wealthy family and grew up on the family estate in Picardy where he became interested in aviculture and established a private zoo. He attended good schools and achieved a doctorate in biology from the Université Lille Nord de France. He served in the French Army during the First World War, a war which devastated the family estate, as well as killing his only surviving brother. Moving to Chateau Clères in Normandy, he created a second zoo, eventually donating it to the Museum National d'Histoire Naturelle in 1967. He went on numerous scientific expeditions to Indochina, particularly Vietnam, as well as to Venezuela, the Guianas and Madagascar.
During the Second World War Delacour lived in the USA, working as a technical adviser at the Bronx Zoo as well as on avian systematics at the American Museum of Natural History. In 1952 he became director of the Los Angeles County Museum of History, Science and Art, retiring in 1960. Thereafter he divided his time seasonally, spending summer at his estate at Clères in France, and wintering in the United States, mainly in Los Angeles.
As well as many papers in the ornithological literature, some books authored or coauthored by Delacour are: