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

McCain followed his father and grandfather, both four-star admirals, into the United States Navy, graduating 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 was almost killed in the 1967 USS Forrestal fire. In October 1967, while on a bombing mission over Hanoi, he was shot down, seriously injured, and captured by the North Vietnamese. He was a prisoner of war until 1973. McCain experienced episodes of torture, and refused 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 and moved to Arizona, where he 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 four times, most recently in 2010. While generally adhering to conservative principles, McCain at times has had a media reputation as a "maverick" for his willingness to disagree with his party on certain 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. McCain has chaired the Senate Commerce Committee, opposed spending that he considered to be pork barrel, and played a key role in alleviating a crisis over judicial nominations.

McCain ran for the Republican presidential nomination in 2000 but lost a heated primary season contest to George W. Bush. He secured the nomination in 2008 after coming back from early reversals, but lost to Democratic candidate Barack Obama in the general election. He subsequently adopted more orthodox conservative stances and attitudes and largely opposed actions of the Obama administration.