His grandson Cory Schenkel said George died on Sunday morning in Boise, Idaho. He was 91.
George Kennedy holding his Oscar (AP)
He had undergone emergency triple bypass surgery in 2002. That same year, he and his late wife moved to Idaho to be closer to their daughter and her family, although he was still involved in occasional film projects.
His biggest acting achievement came in Cool Hand Luke, a 1967 film about a rebellious war hero played by Paul Newman who is bent on bucking the system as a prisoner on a Southern chain gang.
Its theme of rebelling against authority and the establishment helped make it one of the most important films of the tumultuous 1960s.
George played Dragline, the chain-gang boss who goes from Luke’s nemesis to his biggest disciple as Newman’s character takes on folk hero status among fellow inmates.
The film garnered four Academy Award nominations, and George was named best supporting actor.
After the critical and commercial success of Cool Hand Luke, George carved out a niche as one of Hollywood’s most recognisable supporting actors.
George Kennedy, centre, in Dallas (Eric G Gay/AP)
He had parts in several action flicks in the 1970s, played Leslie Nielsen’s sidekick in the Naked Gun spoofs and was JR Ewing’s business rival Carter McKay in Dallas between 1988 and 1991.
One of his strongest supporting roles was in the hit 1970 film Airport, which spurred the run of 1970s’ disaster pictures.
The film spawned several sequels (George was in all of them) and landed George a Golden Globe nomination.
George Kennedy and his Chattanooga Choo Choo co-star Barbara Eden (Al Behrman/AP)
His film career began to take flight when he starred in 1963′s Charade, while his other acting credits in the 1960s included The Dirty Dozen and Guns Of The Magnificent Seven.
George’s last on-screen role was in the 2014 remake of The Gambler, which starred Mark Wahlberg.
George was born in New York in 1925. He started acting at the age of two when he joined a touring company.
George Kennedy – left, with his wife Norma Wurman – at the premiere of The Flight Of The Phoenix (PA)
He enlisted in the Army at 17 and served in the Second World War, opening the first Army Information Office that provided technical assistance to films and TV shows. George spent 16 years in the army and left as a captain.
He made his television debut in The Phil Silvers Show in 1955 and made guest appearances in the Westerns Have Gun, Will Travel, Cheyenne and Gunsmoke.
George, an avid reader, also dabbled in writing and published a couple of murder mysteries.
In later years, he became an advocate for adopted children. He had four adopted children, including his granddaughter Taylor, whose mother, also adopted by George, had become addicted to drugs and alcohol.