Dio, who had been suffering from stomach cancer, was being treated at a hospital in Houston, Texas, according to his website.
His wife Wendy Dio said in a statement her "heart is broken", adding that friends and family were able to say their goodbyes to her husband.
"We so appreciate the love and support that you have all given us," she said. "Please give us a few days of privacy to deal with this terrible loss. Please know he loved you all and his music will live on forever."
Dio rose to fame in 1975 as the first lead singer of Rainbow, the heavy metal band put together by guitarist Ritchie Blackmore, who had just quit Deep Purple.
Dio then replaced Osbourne in Black Sabbath in 1980 with the critically acclaimed album "Heaven And Hell," considered by many critics to be one of the finest heavy metal albums of all time. His on-again, off-again tenure with Black Sabbath touched off an intense debate among fans as to which singer was the true essence of the band — a discussion that lasted until his death.
He also enjoyed a successful solo career with his self-titled band, Dio, in between his three stints with Black Sabbath (1980-82; 1992; and 2007-2009, when the band toured as Heaven And Hell, to differentiate it from Osbourne-led versions of Sabbath).
Many of his most memorable songs revolved around the struggle between good and evil, including his signature tune "Heaven And Hell." He also drew heavily on medieval imagery in songs like "Neon Knights," "Killing The Dragon" and "Stargazer."
"He possessed one of the greatest voices in all of heavy metal, and had a heart to match it," said Twisted Sister guitarist Jay Jay French, whose band toured with Dio since 1983, and was to do so again this summer at European rock festivals. "He was the nicest, classiest person you would ever want to meet."
Dio organized an all-star charity collaboration in 1986 called "Hear N' Aid" to raise money for famine relief in Africa, styled on the successful "We Are The World" campaign of a few years earlier.
His solo hits included "Rainbow In The Dark," "The Last In Line" and "Holy Diver."
This article borrowed from the Daily Telegraph website : www.telegraph.co.uk