Williams, who announced in late 2011 that he had been diagnosed with bladder cancer, died Tuesday at his home in Branson, Mo., his family announced.
The Iowa-born Williams began singing professionally as a boy with his three older brothers in the 1930s, and he went solo when the quartet broke up in the early `50s.
After becoming a regular featured singer on Steve Allen's Tonight" show in 1954, Williams had hits with songs such as Canadian Sunset," Butterfly," Are You Sincere," Hawaiian Wedding Song" and The Village of St. Bernadette."
He continued to turn out hits in the 1960s and `70s, including Can't Get Used to Losing You," Dear Heart," Charade," Music to Watch Girls By" and (Where Do I Begin) Love Story."
The singer hosted The Andy Williams Show" on NBC from 1962 to 1967. After doing three specials a year for two years, he returned to the weekly series from 1969 to 1971.
The Andy Williams Show" won three Emmy Awards, and its casual, sweater-wearing host received two Emmy nominations.
In some cases, people who go on television, their record sales drop off; mine seemed to go up," Williams told the Orlando Sentinel in 1991.
I think it's because the music is kind of soft and easy and it's not jamming down anybody's throat. It's just there and people find it pleasant and like it, and they go out and buy the albums."
The Andy Williams Show" featured established entertainers such as Bing Crosby, Ella Fitzgerald, Jonathan Winters and Phyllis Diller as well as newer talents such as Linda Ronstadt, the Mamas and the Papas, Elton John and the Jackson 5.
Williams also regularly featured the Osmond Brothers, who were initially billed as a youthful barbershop harmony group from Ogden, Utah" when they debuted on the show in 1962.
A popular feature of Williams' TV program was the annual Christmas show, on which he would be surrounded by his own family members.
So popular were the Christmas shows that when the weekly series went off the air, Williams told the Chicago Sun-Times in 2000, we got thousands of pieces of mail" asking him to come back, which he did by hosting annual Christmas TV specials for many years. He later did Christmas shows in theaters around the country.
Williams said he never tired of singing Moon River," whose melody he considered beautiful" and whose lyrics he called timeless."
You wouldn't believe how 'Moon River' became a hit," he said in a 1989 interview with the Chicago Tribune. I was having dinner with [songwriters] Henry Mancini and Johnny Mercer, who had just finished recording the movie 'Breakfast at Tiffany's,' with Audrey Hepburn singing 'Moon River' out on the balcony with a guitar.
So Mancini and Mercer played this song for me, which I thought was great. But my record company was really into singles then, and they said: 'I don't think phrases like 'my Huckleberry friend' will make it with the kids — they won't know what it means.'"
But about four weeks before the 1962 Academy Awards program, he recalled, I was invited to sing 'Moon River' on the Oscars show, and Columbia Records decided we ought to rush a 'Moon River' album into the stores, because that tune looked like a shoo-in for the 'best song' Oscar.
So they quickly put out an album, had it in the stores on the day of the Oscars, and the next morning it sold 500,000 copies."
The son of a railroad mail clerk, Williams was born Dec. 3, 1927, in Wall Lake, Iowa. As a boy, he began singing with his three older brothers — Bob, Don and Dick — in the local Presbyterian church choir.
The very first time he heard his four sons harmonize together, my dad became a man with a dream and a mission in life, convinced that we had a future as professional singers," Williams wrote in his 2009 memoir Moon River and Me."