Daniel Ken Inouye (September 7, 1924 – December 17, 2012) was an American attorney, soldier, and politician who served as a United States senator from Hawaii from 1963 until his death in 2012. Beginning in 1959, he was the first U.S. Representative for the State of Hawaii, and a Medal of Honor recipient. A member of the Democratic Party, he also served as the president pro tempore of the United States Senate from 2010 until his death. Inouye was the highest-ranking Asian-American politician in U.S. history, until Kamala Harris became vice president in 2021. Inouye also chaired various senate committees, including those on Intelligence, Indian Affairs, Commerce, and Appropriations.

Inouye fought in World War II as part of the 442nd Infantry Regiment. He lost his right arm to a grenade wound and received several military decorations, including the Medal of Honor (the nation's highest military award). He later earned a J.D. degree from George Washington University Law School. Returning to Hawaii, Inouye was elected to Hawaii's territorial House of Representatives in 1953, and was elected to the territorial Senate in 1957. When Hawaii achieved statehood in 1959, Inouye was elected as its first member of the House of Representatives. He was first elected to the U.S. Senate in 1962. He never lost an election in 58 years as an elected official, and he exercised an exceptionally large influence on Hawaii politics.

Inouye was the second Asian American senator, following Hawaii Republican Hiram Fong. Inouye was the first Japanese American to serve in the U.S. House of Representatives, and the first to serve in the U.S. Senate. Because of his seniority, Inouye became president pro tempore of the Senate following the death of Robert Byrd on June 29, 2010, making him third in the presidential line of succession after the Vice President and the Speaker of the House of Representatives. At the time of his death, Inouye was the most senior sitting U.S. senator, the second-oldest sitting U.S. senator (seven and a half months younger than Frank Lautenberg of New Jersey), and the last sitting U.S. senator to have served during the presidencies of John F. Kennedy, Lyndon B. Johnson, and Richard Nixon.

Inouye was a posthumous recipient of the Presidential Medal of Freedom and the Order of the Paulownia Flowers. Among other public structures, Honolulu International Airport has since been renamed Daniel K. Inouye International Airport in his memory.