Williams, 84, began his singing career as a child in a quartet with his brothers, but rose to stardom as a solo act starting in the 1950s.
"The Andy Williams Show," a weekly television variety program that ran for nine years on NBC starting in 1962, and a dozen TV specials from 1959 through 1987 made Williams a household name in the United States.
He spent the last 20 years of his career performing on his own stage at his Moon River Theatre in Branson.
"Moon River" became his theme song after he performed it at the 1962 Academy Awards, where it won an Oscar for best song in a movie. Audrey Hepburn sang the Johnny Mercer and Henry Mancini composition in the film "Breakfast at Tiffany's."
Williams' recording career reached superstar status in 1963 when his album "Days of Wine and Roses" spent 16 weeks at the top of the U.S. music charts.
His variety TV show, which promoted the careers of many other artists including the Osmond Brothers, won high ratings and three Emmys.
He hosted five Christmas television specials, between 1973 and 1985, along with seven other television specials, the first in 1959 and the last in 1987.
Williams, who also had a home in La Quinta, California, is survived by his wife of 21 years, Debbie, and his three children with French singer Claudine Longet -- Robert, Noelle and Christian.
He was married to Longet from 1961 until their divorce in 1975. A year later, she was charged with the fatal shooting of her boyfriend, Olympic skier Spider Sabich.
Williams stood by Longet, who claimed the shooting was accidental. She spent a month in jail.
Williams' Branson theater was the first non-country venue built in the small Missouri tourist mecca.
He was born on December 3, 1927, in Wall Lake, Iowa, where he began singing with brothers Bob, Dick and Don in a Presbyterian church choir led by their parents.
Williams was just eight when he made his professional singing debut with the Williams Brothers Quartet. The brothers were regular performers on radio station WHO's "Iowa's Barn Dance Show" in Des Moines, Iowa. Their popularity grew, taking the brothers to national stations, including WLS in Chicago and WLW in Cincinnati.
CNN's Denise Quan contributed to this report.
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