June performed and recorded with her husband for 40 years
June Carter Cash, the singer and wife of Johnny Cash, has died after suffering complications from heart surgery.
Carter Cash, 73, who won three Grammy awards - including two for duets with her husband - had an operation to replace a valve on 7 May.
Her husband and family members were at her bedside at the Baptist Hospital in Nashville when she died on Thursday.
She was described as one of "the pioneering women in country music" by the Country Music Association.
From an established country music dynasty, she married Johnny Cash in 1968 and toured and performed with him for 40 years.
The couple won Grammys for the duets Jackson in 1967 and If I Were A Carpenter in 1970, and co-wrote Cash's 1963 number one single Ring of Fire, about falling in love with him.
Johnny Cash with his wife (centre) and daughter Roseanne Cash
Carter Cash also won a Grammy for best traditional folk album for her last solo release, Press On, in 1999.
"People talk about Loretta Lynn and Tammy Wynette when it comes to pioneering women in country music," Ed Benson, executive director of the Country Music Association said.
"But they very seldom mention June, somewhat because she got married to Johnny Cash."
Mrs Carter Cash was the daughter of early country singer Maybelle Carter and the mother of country rock star Carlene Carter.
Maybelle Carter was a member of The Carter Family, one of country music's first hit acts who made one of the first country recordings in 1927.
When the original family group split, the 10-year-old June and sisters Helen and Anita were recruited to sing with Mother Maybelle and the Carter Sisters.
She was married to country singer Carl Smith in the 1950s but later moved to New York to study acting.
The couple in the Blue Room of the White House in 1970
In 1961, she turned down an offer to appear on a variety show, for which Woody Allen was a writer, in favour of going on tour with Johnny Cash.
The couple married seven years later after Cash proposed to her on stage on London, Ontario, Canada.
In 1987, she described her husband as "probably the most unusual, fine, unselfish person I've known".
Johnny Cash, who is 71, has endured health problems of his own, going in an out of hospital during the last few years with pneumonia and bronchitis.
In the sleeve notes for his latest album, The Man Comes Around, he described his wife as "a soft, fluffy Mama Bear".
And he described how she stuck with him through years of amphetamine abuse in his 1997 autobiography.
"June said she knew me - knew the kernel of me, deep inside, beneath the drugs and deceit and despair and anger and selfishness, and knew my loneliness," he wrote.
"She said she could help me... If she found my pills, she flushed them down the toilet.
"And find them she did - she searched for them, relentlessly."
Mrs Carter Cash's funeral will be private, with no details expected to be released.