Andy Williams, the “Moon River” crooner who helped define American popular music in the 1960s and 1970s through his Christmas albums, nightclub performances and television variety show, has died. He was 84.

Williams died Tuesday at his home in Branson, Mo., his publicist, Paul Shefrin, said, citing the family. The cause was bladder cancer.

Since 1992, Williams made his home mostly in Branson, where he built, ran and performed at the 2,000-seat Moon River Theatre. During a concert there last November, he announced he had bladder cancer and vowed to return in 2012 to celebrate the Christmas season and to mark his 75th year in show business.

Williams became closely associated with Christmas through the song “It’s the Most Wonderful Time of the Year,” which he recorded and released in 1963, and through the television specials he hosted each holiday season – always with his family as special guests, and always in a colorful sweater that practically screamed yuletide cheer.

“The show I always enjoyed doing above all others was the Christmas show, and it was the one that the audiences loved the most, too,” Williams wrote in “Moon River and Me,” his 2009 memoir.

“The Andy Williams Show,” a weekly variety show, ran on NBC from 1962 to 1967, and again from 1969 to 1971. It helped make stars of the Osmond Brothers, whose 1963 performance was so popular that they were asked to become regulars.

Eighteen of Williams’s albums were certified gold by the Recording Industry Association of America, meaning they each had sold more than 500,000 copies. Three others sold more than 1 million copies each, achieving platinum status: “The Andy Williams Christmas Album” (1963), “Merry Christmas” (1965) and “Love Story” (1971).

It was “Moon River,” recorded in 1961 just after he signed with Columbia Records, that became his theme song. He sang the first bars – “Moon river, wider than a mile, I’m crossing you in style, someday” – to open his television show.

He and his first wife, the former Claudine Longet – who appeared with their three children, Christian, Robert and Noelle, on his annual Christmas specials – split up in 1969 and divorced in 1975.

In 1977, when Longet faced a felony charge of reckless manslaughter in the shooting death of her boyfriend, skier Vladimir “Spider” Sabich, Williams attended the trial in support of his ex-wife. Longet was convicted of a lesser charge. She was sentenced to 30 days in jail.

Williams’ second marriage, in 1991, was to the former Debbie Haas, who survives him.

Though he was a Republican, Williams became close friends with Robert Kennedy in the 1960s and was traveling with his presidential campaign on June 5, 1968, when Kennedy was assassinated in the ballroom of the Ambassador Hotel in Los Angeles.

Williams sang “The Battle Hymn of the Republic” at the memorial service for Kennedy at St. Patrick’s Cathedral in New York – which he called “the hardest thing I’ve ever done.”