Police say Welch was found dead by his wife after shooting himself in the chest at their Nashville home at around 12.15pm local time today.
The Californian musician had had health issues recently, according to police spokesman Don Aaron, who confirmed that Welch left a suicide note.
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Suicide: Former Fleetwood Mac member Bob Welch was found dead today after shooting himself in the chest
The spokesman would not elaborate on specific details regarding Welch's health - but added that there was no evidence of foul play.
Welch, who also had a solo career, was a guitarist and vocalist for Fleetwood Mac from 1971 to 1974 and worked on albums such as Future Games and Bare Trees.
Ailing: Welch, pictured here in a 1995 documentary, had apparently suffered from health problems of late
He formed the British rock group Paris in 1976, and had hits including Sentimental Lady in 1977 and Ebony Eyes in 1978.
Fleetwood Mac's Christine McVie and Lindsey Buckingham did backing vocals on Sentimental Lady.
Fleetwood Mac's career took off in the mid-1970s after Welch left the band.
Dreams was a Number 1 hit in 1977, and Don't Stop hit the top of the charts the same year.
It later became the anthem for Bill Clinton's presidential campaign. Hold Me was a hit in 1982 and Little Lies in 1987.
Welch, a native of Los Angeles, scored his biggest hit with Sentimental Lady, which reached No. 8 on the Billboard chart.
His other singles included Precious Love in 1979 and Hot Love, Cold World in 1978.
Welch fell out with his former band mates after suing the group in 1994 for unpaid royalties, which led to his exclusion from the group's Rock and Roll Hall of Fame induction in 1998.
'It basically comes down to the fact that they don't like me anymore,' he told The Plain Dealer of Cleveland at the time.
'I guess they can do what they want. I could understand it if I had been a sideman for a year. But I was an integral part of that band... I put more of myself into that band than anything else I've ever done.'
Devastated: Longtime Fleetwood Mac singer Stevie Nicks today told The Associated Press that Welch's death hit her hard
Longtime Fleetwood Mac singer Stevie Nicks today told The Associated Press that Welch's death hit her hard.
'The death of Bob Welch is devastating... I had many great times with him after Lindsey and I joined Fleetwood Mac. He was an amazing guitar player - he was funny, sweet - and he was smart. I am so very sorry for his family and for the family of Fleetwood Mac - so, so sad.'
As a songwriter, Welch had his songs recorded by Kenny Rogers, Sammy Hagar, the Pointer Sisters and others.
In 1999 he released a CD, Bob Welch Looks at Bop, a salute to bebop music in the 1940s.
Heyday: Welch, centre, was in the band between 1971 and 1974, and was a guitarist and vocalist. Pictured here in 1973 with (from left) Bob Weston, Christine McVie, John McVie and Mick Fleetwood
In an interview with The Tennessean in 2003, Welch said he never dreamed he'd be remembered for much.
'I just wanted to play guitar in a good band,' he said. 'I wanted to make the music I love. I wanted to travel the world and have adventures.'
Welch also said 'music is disposable now. It doesn't have the emotional impact anymore. That's sad.'
He had lived in Nashville since the 1990s.
Welch is the second member of Fleetwood Mac to die this year. In January, another former guitarist for the band, Bob Weston, died in London from a gastrointestinal haemorrhage, at age 64.
Former bandmates: Fleetwood Mac circa 1972/1973, Welch is seen in the middle
