Paul Belloni Du Chaillu (July 31, 1831 (disputed) – April 29, 1903) was a French-American traveler, zoologist, and anthropologist. He became famous in the 1860s as the first modern European outsider to confirm the existence of gorillas, and later the Pygmy people of central Africa. He later researched the prehistory of Scandinavia.

There are conflicting reports of both the year and place of Du Chaillu's birth. The year is variously given as 1831 (the consensus of modern scholars), 1835, or 1839; the date when given is July 31. Accounts usually cite either Paris or New Orleans as his likely place of birth. A contemporary obituary quotes a statement made by Du Chaillu referring to "the United States, my country by adoption, and ... France, my native land." His entry in the 1901-1902 edition of Marquis Who's Who — which was based on information he supplied directly to the editors — says 1838 in New Orleans. His grave marker identifies his place of birth as Louisiana, and the year as 1839.

Edward Clodd, Du Chaillu's friend, told the story differently in his memoirs. Clodd mentioned New York as another claimed location, but asserted that Du Chaillu's true birthplace was the French Indian Ocean island territory of Île Bourbon (now called Réunion). He further claimed that du Chaillu's mother was a mulatto woman. In 1979, historian Henry H. Bucher presented evidence to back Clodd's view, including records of Du Chaillu's father. Bucher argued that Du Chaillu, as a member of the European scientific community, would have tried to obfuscate or conceal the family history that would have labeled him a quadroon. In the 19th century atmosphere of scientific racism, great apes and Sub-Saharan Africans were often considered to both have small cranial capacity, and thus be innately unable to achieve civilization; Du Chaillu's credibility as a scientist and explorer would have suffered as a result. Indeed, comments in a letter by Du Chaillu's contemporary, the ethnologist of Africa Mary Kingsley, indicate that at least some scientists who thought poorly of Du Chaillu knew of his ancestry or other information presumed to be disqualifying.

In his youth, he accompanied his father, a French trader in the employment of a Parisian firm, to the west coast of Africa where, at a station on the Gabon, he was educated by missionaries and acquired an interest in and knowledge of the country, its natural history, its natives, and their languages before emigrating to the U.S. in 1852.

He was sent in 1855 by the Academy of Natural Sciences at Philadelphia on an African expedition. Until 1859, he explored the regions of West Africa in the neighborhood of the equator, gaining considerable knowledge of the delta of the Ogooué River and the estuary of the Gabon. During his travels from 1856 to 1859, he observed numerous gorillas, known to non-locals in prior centuries only from an unreliable and ambiguous report credited to Hanno the Navigator of Carthage in the 5th century BC and known to scientists in the preceding years only by a few skeletons. He brought back dead specimens and presented himself as the first white European person to have seen them.

A subsequent expedition, from 1863 to 1865, enabled him to confirm the accounts given by the ancients of a pygmy people inhabiting the African forests. Du Chaillu sold his hunted gorillas to the Natural History Museum in London. His efforts to keep captive baby gorilla infants alive were unsuccessful, as the infants proved to be "morose," "ill-tempered," and subject to "a feeling of revenge." He sold his "cannibal skulls" to other European collections; a fine cased group shot by Du Chaillu may be seen in the Ipswich Museum in Suffolk, England.

Narratives of both expeditions were published, in 1861 and 1867 respectively, under the titles Explorations and Adventures in Equatorial Africa, with Accounts of the Manners and Customs of the People, and of the Chace of the Gorilla, Crocodile, and other Animals; and A Journey to Ashango-land, and further penetration into Equatorial Africa. While in Ashango Land in 1865, he was elected King of the Apingi [fr] tribe. A later narrative, The Country of the Dwarfs was published in 1872.

At the time, he was in great demand on the public lecture circuits of New York, London, and Paris. Although there were initial challenges of his accounts, they came to be accepted, although Encyclopædia Britannica speculated that "possibly some of the adventures he described as happening to himself were reproductions of the hunting stories of natives."