John Sidney McCain III (born August 29, 1936) is the senior United States Senator from Arizona and presidential nominee of the Republican Party in the 2008 presidential election.

McCain graduated from the U.S. Naval Academy in 1958. He became a naval aviator, flying ground-attack aircraft from aircraft carriers. During the Vietnam War, he nearly lost his life in the 1967 USS Forrestal fire. In October 1967 while on a bombing mission over Hanoi, he was shot down, badly injured, and captured by the North Vietnamese. He was a prisoner of war until 1973, experiencing episodes of torture and refusing an out-of-sequence early repatriation offer; his war wounds left him with lifelong physical limitations.

He retired from the Navy as a captain in 1981, moved to Arizona, and entered politics. Elected to the U.S. House of Representatives in 1982, he served two terms, and was then elected to the U.S. Senate in 1986, winning re-election easily in 1992, 1998, and 2004. While generally adhering to conservative principles, McCain at times has had a media reputation as a "maverick" for disagreeing with his party on several key issues. After being investigated and largely exonerated in a political influence scandal of the 1980s as a member of the "Keating Five," he made campaign finance reform one of his signature concerns, which eventually led to the passage of the McCain-Feingold Act in 2002. He is also known for his work towards restoring diplomatic relations with Vietnam in the 1990s, and for his belief that the war in Iraq should be fought to a successful conclusion in the 2000s. McCain has chaired the Senate Commerce Committee, has opposed pork barrel spending, and played a key role in alleviating a crisis over judicial nominations.

McCain lost his bid for the Republican nomination in the 2000 presidential election to George W. Bush. He ran again for the Republican presidential nomination in 2008, and gained enough delegates to become the party's presumptive nominee in March 2008. McCain was formally nominated at the 2008 Republican National Convention in September 2008, together with his chosen running mate from Alaska, Governor Sarah Palin.