Yōsuke Matsuoka (松岡 洋右, Matsuoka Yōsuke^?, March 3, 1880 – June 26, 1946) was a Japanese diplomat and Minister of Foreign Affairs of the Empire of Japan during the early stages of World War II. He is best known for his defiant speech at the League of Nations in 1933, ending Japan's participation in that organization. He was also one of the architects of the Tripartite Pact and the Japanese–Soviet Neutrality Pact in the years immediately prior to the outbreak of war.

Matsuoka was born as the fourth son to a shipping magnate in Kumage District, Yamaguchi prefecture (now part of the city of Hikari). At the age of 11, his father’s business went bankrupt, and Matsuoka was sent to the United States with a cousin in 1893 under the sponsorship of Methodist missionaries to study English. He settled in Portland, Oregon, living initially at the Methodist Mission, and was subsequently taken into the household of the widower William Dunbar, which included Dunbar's son Lambert, and Dunbar's sister, Mrs. Isabelle Dunbar Beveridge. Mrs. Beveridge served as a foster mother to Matsuoka and helped him adjust to American society. Matsuoka's affection for her lasted well after he returned to Japan. She died in 1906.