Jacques-Yves Cousteau, AC (/kuːˈstoʊ/, also UK: /ˈkuːstoʊ/, French: [ʒak iv kusto]; 11 June 1910 – 25 June 1997) was a French naval officer, oceanographer, filmmaker and author. He co-invented the first successful open-circuit self-contained underwater breathing apparatus (SCUBA), called the Aqua-Lung, which assisted him in producing some of the first underwater documentaries.

Cousteau wrote many books describing his undersea explorations. In his first book, The Silent World: A Story of Undersea Discovery and Adventure, Cousteau surmised the existence of the echolocation abilities of porpoises. The book was adapted into an underwater documentary called The Silent World. Co-directed by Cousteau and Louis Malle, it was one of the first films to use underwater cinematography to document the ocean depths in color. The film won the 1956 Palme d'Or at the Cannes Film Festival and remained the only documentary to do so until 2004 (when Fahrenheit 9/11 received the award). It was also awarded the Academy Award for Best Documentary in 1957.

From 1966 to 1976, he hosted The Undersea World of Jacques Cousteau, a documentary television series. A second documentary series, The Cousteau Odyssey, ran from 1977 to 1982 on public television stations.

"The sea, the great unifier, is man's only hope. Now, as never before, the old phrase has a literal meaning: We are all in the same boat."

Cousteau was born on 11 June 1910, in Saint-André-de-Cubzac, Gironde, France, to Daniel Cousteau and Élisabeth Duranthon. He had one brother, Pierre-Antoine. Cousteau completed his preparatory studies at the Collège Stanislas in Paris. In 1930, he entered the École navale and graduated as a gunnery officer. However, an automobile accident, which broke both his arms, cut short his career in naval aviation. The accident forced Cousteau to change his plans to become a naval pilot, so he then indulged his passion for the ocean.

In Toulon, where he was serving on the Condorcet, Cousteau carried out his first underwater experiments, thanks to his friend Philippe Tailliez who in 1936 lent him some Fernez underwater goggles, predecessors of modern swimming goggles. Cousteau also belonged to the information service of the French Navy, and was sent on missions to Shanghai and Japan (1935–1938) and in the USSR (1939).

On 12 July 1937, he married Simone Melchior, his business partner, with whom he had two sons, Jean-Michel (born 1938) and Philippe (1940–1979). His sons took part in the adventures of the Calypso. In 1991, six months after his wife Simone's death from cancer, he married Francine Triplet. They already had a daughter Diane Cousteau (born 1980) and a son, Pierre-Yves Cousteau (born 1982, during Cousteau's marriage to his first wife).

The years of World War II were decisive for the history of diving. After the armistice of 1940, the family of Simone and Jacques-Yves Cousteau took refuge in Megève, where he became a friend of the Ichac family who also lived there. Jacques-Yves Cousteau and Marcel Ichac shared the same desire to reveal to the general public unknown and inaccessible places—for Cousteau the underwater world and for Ichac the high mountains. The two neighbors took the first ex-aequo prize of the Congress of Documentary Film in 1943, for the first French underwater film: Par dix-huit mètres de fond (18 meters deep), made without breathing apparatus the previous year in the Embiez islands in Var, with Philippe Tailliez and Frédéric Dumas, using a depth-pressure-proof camera case developed by mechanical engineer Léon Vèche, an engineer of Arts and Measures at the Naval College.