"Johnny died due to complications from diabetes, which resulted in respiratory failure," said Cash's manager, Lou Robin, in a press release issued by Baptist Hospital in Nashville.
He had been released from Baptist on Wednesday where he had spent two weeks being treated for an unspecified stomach ailment.
Cash's career spanned country, rock and folk.
"Johnny Cash was a giant," Rolling Stone magazine contributing editor Anthony DeCurtis told CBS Radio News. "Johnny Cash was in there at the beginning with Elvis Presley and Jerry Lee Lewis and Sam Phillips at Sun Records. Making a record like 'I Walk The Line' really helped define the early days of rock 'n roll."
"What he really was able to do was take country music to the world, to people who had perhaps said they didn't like country music," Radio and Records Country Editor Lon Helton told CBS News Correspondent Stephan Kaufman.
Known worldwide as "The Man in Black," Cash had dozens of hit records. Songs like "Folsom Prison Blues," "I Walk the Line," and "Sunday Morning Coming Down" defined Cash's persona: a haunted, dignified, resilient spokesman for the working man and downtrodden.
"He was one of these figures that everyone seemed to like," said DeCurtis. "He was a populist figure. So regardless of what side of a particular issue you were on, you found something in Johnny Cash that reflected your own vision of life."
Cash's deeply lined face fit well with his unsteady voice, which was limited in range but used to great effect to sing about prisoners, heartaches, and tales of everyday life. He wrote much of his own material, and was among the first to record the songs of Bob Dylan and Kris Kristofferson.
"One Piece at a Time" was about an assembly line worker who built a car out of parts stolen from his factory. "A Boy Named Sue" was a comical story of a father who gives his son a girl's name to make him tough. "The Ballad of Ira Hayes" told of the drunken death of an American Indian soldier who helped raised the American flag at Iwo Jima during World War II, but returned to harsh racism in America.
Cash said in his 1997 autobiography "Cash" that he tried to speak for "voices that were ignored or even suppressed in the entertainment media, not to mention the political and educational establishments."
Cash's career spanned generations, with each finding something of value in his simple records, many of which used his trademark "boom-chicka-boom" rhythm.
He never stopped working and his video "Hurt" — a cover of a song by Nine Inch Nails — was nominated for seven MTV Video Music awards, winning one at the ceremonies last month.
John R. Cash was born Feb. 26, 1932, in Kingsland, Ark., one of seven children. When he was 12, his 14-year-old brother and hero, Jack, died after an accident while sawing oak trees into fence posts. The tragedy had a lasting impact on Cash, and he later pointed to it as a possible reason his music was frequently melancholy.
Cash launched his career in Memphis, performing on radio station KWEM. He auditioned with Sun Records, ultimately recording the single "Hey Porter," which became a hit.
Cash recorded theme albums celebrating the railroads and the Old West, and decrying the mistreatment of American Indians. Two of his most popular albums were recorded live at prisons. Along the way he notched 14 No. 1 country music hits.
Because of Cash's frequent performances in prisons and his rowdy lifestyle early in his career, many people wrongly thought he had served prison time. He never did, though he battled addictions to pills on and off throughout his life.
"Life has to slap you around a little bit and then you really understand what country music is all about, and I think Johnny Cash embodied that in his very being," added Helton, also host of Westwood One's "Country Countdown USA" show. "Just looking at him, you knew that this guy had lived and he'd lived the songs and he was kind of an everyman as well."
CBSNews.com and Westwood One are both Viacom-related operations.
Cash was a peer of Elvis Presley when rock 'n' roll was born in Memphis in the 1950s, and he scored hits like "Cry! Cry! Cry!" during that era. He had a longtime friendship and recorded with Dylan, who has cited Cash as a major influence.
He won 11 Grammys - most recently in 2003, when "Give My Love To Rose" earned him honors as best male country vocal performance and numerous Country Music Association awards. He was elected to the Country Music Hall of Fame in 1980 and inducted into the Rock and Roll Hall of Fame in 1992.
His second wife, June Carter Cash, was a singing legend in her own right, as is daughter Roseanne Cash. June Carter Cash, who co-wrote Cash's hit "Ring of Fire" and partnered with her husband in hits such as "Jackson," died this past May.
The late 1960s and '70s were Cash's peak commercial years, and he was host of his own ABC variety show from 1969-71. In later years, he was part of the Highwayman supergroup with Waylon Jennings, Willie Nelson and Kristofferson.
In the 1990s, he found a new artistic life recording with rap and hard rock producer Rick Rubin on the label American Recordings. And he was back on the charts in with the 2002 album "American IV: the Man Comes Around."
He also wrote books including two autobiographies, and acted in films and television shows.
In his 1971 hit "Man in Black," Cash said his black clothing symbolized the downtrodden people in the world. Cash had been "The Man in Black" since he joined the Grand Ole Opry at age 25.
"Everybody was wearing rhinestones, all those sparkle clothes and cowboy boots," he said in 1986. "I decided to wear a black shirt and pants and see if I could get by with it. I did and I've worn black clothes ever since."
Cash had battled a disease of the nervous system, autonomic neuropathy, and pneumonia in recent years and was once diagnosed with a disease called Shy-Drager's syndrome, a diagnosis that was later deemed to be erroneous.