Eagles guitarist Glenn Frey has died at the age of 67, the band has announced.
He died in New York City on Monday from complications arising from rheumatoid arthritis, colitis and pneumonia.
"Words can neither describe our sorrow, nor our love and respect for all that he has given to us," his family and fellow band members said.
The Eagles were one of the most successful bands of the 1970s, with multiple hit singles, including Hotel California in 1976.
Frey co-founded the Eagles in 1971 with Don Henley, Bernie Leadon and Randy Meisner.
He co-wrote Hotel California with Henley and Don Felder, and composed a number of the band's biggest songs on his own, including Heartache Tonight and Lyin' Eyes.
The Eagles notched up more than 150 million album sales worldwide, with Hotel California and their greatest hits among the best selling in history.
Tributes have been paid on social media, with country star Tim McGraw writing: "His music was personally inspirational, his impact immeasurable, his legacy timeless. #glennfrey #heartachetonight"
Paul Stanley from Kiss added: "SHOCKED to report the death of GLENN FREY. Eagle & brilliant songwriter."
Singer Ryan Adams wrote: "RIP, Glenn Frey. Travel to the stars safely, bro", while Huey Lewis called him " a really good guy. Talented, funny, cynical and sweet".
Flawless harmonies: Mark Savage, Music reporter
The Eagles were one of the great forces of 1970s rock. They may not have had the dynamics of Led Zeppelin or the drama of Fleetwood Mac, but they dominated the airwaves. AM radio would play the hits, filled with flawless harmonies, while FM stations would spin the longer, unedited album cuts.
Frey emerged as one of the band's chief songwriters, the Lennon to Don Henley's McCartney. He penned their breakout hit Take It Easy - a song as laid back as its title suggests - with Jackson Browne. But later singles, including Take It To The Limit and Hotel California, were group efforts, while the two front men would share vocal duties - Frey's supple tones a perfect counterpoint to Henley's rasp.
In the US, they scored five number one singles and four number one albums; while their greatest hits sold 30 million copies.
"It boggles the mind somewhat," Frey told Rolling Stone in 2012. "But as long as I keep taking out the garbage and cleaning up after the dogs and taking the kids to school, I'll have perspective."
Nonetheless, success took its toll on the band. Frey used to describe their break-up in two words - "Hotel California" - explaining that the pressure of following up that record tore the band apart.
In 1980, Henley famously said the Eagles would reform "when hell freezes over". Fourteen years later, that became the title of the band's comeback album, as the old friends made amends.
"He was like a brother to me; we were family, and like most families, there was some dysfunction," Henley said in a statement.
"But, the bond we forged 45 years ago was never broken, even during the 14 years that the Eagles were dissolved."
After the Eagles' acrimonious split in 1980, Frey enjoyed success as a solo artist, most notably with The Heat is On, recorded for the 1984 film Beverly Hills Cop.
The band reunited in 1994 and became a hugely popular touring act.