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 at Villiers near Amiens where he was fascinated by the orchids and ornamental birds in the castle park. With the money he received from his parents, he established a private zoo in Picardy. He attended good schools in Paris where he spent time in the natural history museum and received 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. He was so shocked by the inhumanity that he swore not to have a family and moved to England for its peace. He however decided to return to France and bought the Chateau Clères in Normandy where he set about making a menagerie. It was so well known that the 9th International Ornithological Congress was held in 1938 in the nearby town of Rouen. One of the visitors to his aviary was the Governor General of the French colony of Indochina. On his invitation, he went on numerous scientific expeditions to Indochina, particularly Vietnam,^[1] as well as to Venezuela, the Guianas and Madagascar.

During the Second World War Chateau Clères was bombed by the German Luftwaffe on 7 June 1940. Most of his library, animals in his collection and the castle were destroyed. He escaped and was saved by Belgians and Frenchmen and he escaped to Vichy. Erwin Stresemann, a good friend and admirer of Delacour heard of the fate of the zoo and attempted to ensure the safety of the remaining animals through the Wehrmacht. Delacour meanwhile fled through Casablanca, Rabat, Tangier and Lisbon, reaching New York on Christmas Day 1940. His American friends found him a job at the Bronx Zoo and the Museum of Natural History at New York. Delacour lived in the United States, working as a technical adviser for the New York Zoological Society (now known as the Wildlife Conservation Society) 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. After the war ended he divided his time seasonally, spending every summer from 1946 at his estate at Clères where he rebuilt his zoo. It was opened in May 1947 with the French Prime Minister taking part in the inauguration. The collection was eventually donated to the Museum National d'Histoire Naturelle in 1967. Delacour spent his winters in the United States, mainly in Los Angeles where he served from 1952 to 1960 as the director of the County Museum of History, Science and Art. In his autobiography he wrote that he believed that humans would eventually annihilate all life on earth.^[1][2]

Delacour is commemorated in the scientific name of a species of Southeast Asian snake, Plagiopholis delacouri.^[3]