The new was confirmed by his family on the musician’s Facebook page, saying that he passed away yesterday afternoon on what was his birthday.
The message reads: “It is with a heavy heart writing this, today is my dad's 66th birthday. He passed away earlier this afternoon.
“He was a brilliant, energetic, loving and most carefree person and the first man I ever loved. Everyone he came in contact with loved him – no adored him.
“I will keep everyone posted on his celebration of life. I appreciate everyone's thoughts and prayers as his family grieves and processes everything at this time.”
Chapman was born in Cardiff on June 9, 1954, and made his first mark in the music world with Skid Row in 1971, but left in 1972.
Chapman joined UFO in 1974 and toured with them in support of their third studio album Phenomenon. However, his first tenure with the band didn’t last, and Chapman departed the following year to form Lone Star with Kenny Driscoll, Tony Smith, Ray Jones, Jim Matthews, Pete Hurley and Dixie Lee.
Chapman played on their self-titled debut album in 1976 and 1977’s Firing On All Six.
He went on to rejoin UFO in 1978 and played on the studio albums No Place To Run, The Wild, The Willing And The Innocent, Mechanix and Making Contact.
Following UFO’s split in 1983, Chapman hooked up with the band’s former bassist Pete Way in Waysted, playing on 1985’s The Good the Bad the Waysted and Save Your Prayers the following year.
No cause of death has been made public.
Tributes from across the rock world have begun to come in, with UFO saying: "We send our deepest sympathy to the family and friends of Paul 'Tonka' Chapman, who died yesterday on his 66th birthday. Paul's son broke the tragic news on Paul's Facebook page yesterday evening. R.I.P. Tonka."
Former Motorhead guitarist Phil Campbell said: "Just woke up to sad news of Paul Chapman passing. He was my main influence on guitar for many years and a brilliant bloke. Thoughts are with his family."
John Corabi called Chapman a "lovely gentleman and a great guitar player," adding: "I had the great fortune of meeting him in Philadelphia, and Los Angeles, and he was nothing short of amazing to a young dreamer. 66 is much too young."
Posting a live version of Lettin’ Go, rock broadcaster Eddie Trunk said: “Listening to Paul Chapman all night. So many great songs he played on and co-wrote in his era. Such a great player.”
We send our deepest sympathy to the family and friends of Paul Tonka Chapman, who died yesterday, on his 66th birthday. Paul's son broke the tragic news on Paul's Facebook page yesterday evening. R.I.P. Tonka pic.twitter.com/JI0XAWOVBSJune 10, 2020
Just woke up to sad news of Paul Chapman passing. He was my main influence on guitar for many years and a brilliant bloke. Thoughts are with his family. RIP Tonka pic.twitter.com/h993Yj3uOcJune 10, 2020
R.I.P. Mr. Paul Chapman!!!! Lovely gentleman and great guitar player!!! I had the great fortune of meeting him in Philadelphia, and L.A., and he was nothing short of amazing to a young dreamer!!!! 66 is much too young!!! pic.twitter.com/ne3bV1I0rpJune 10, 2020
Listening to Paul Chapman @UFO_rockband all night. Soooo bummed. So many great songs he played on & co wrote in his era. Such a great player. Just found this live version of Lettin Go. What a band! RIP Tonka. https://t.co/3UT2YpoeNzJune 10, 2020