The Fahnestock South Sea Expeditions were three scientific expeditions to the Pacific Ocean during 1935–1937, 1940 and 1941, organised and led by brothers Sheridan and Bruce Fahnestock. The Fahnestocks collected plant and animal specimens for museums in the United States, made recordings of traditional songs and music from Pacific Islands, and on the third expedition collected intelligence for the United States armed forces after the outbreak of World War 2.