Injury forces Wales's Evans into retirement
The 32-year-old second row made his Wales debut in 2006 and won the last of his 33 caps nearly three years ago.
Evans was a member of Wales's Six Nations Grand Slam-winning squads in 2008 and 2012 and also helped them take the 2013 Six Nations title.
He joined south-west club Bristol from Welsh regional side Ospreys in 2014.
"I'm deeply saddened to end my professional career now," Evans told Bristol's website.
"However, the knee injury I suffered whilst playing for Bristol prevents me from achieving full fitness and will permanently affect my capability to perform.
"While I'm sad that my playing career has come to an end, I'm looking forward to the next chapter and exploring new opportunities. I've been fortunate enough to have an incredible career.
"I'm honoured to have had the opportunity to represent my country, winning successive Six Nations titles. I'm grateful to the Ospreys and Bristol – two fantastic clubs where I have met great people and hold fond memories," added Evans, also a member of the victorious 2013 British and Irish Lions squad in Australia.
Bristol's acting coach Mark Tainton said: "We thank Ian and wish him the best of luck for the future.
"Ian helped Bristol to promotion in 2016 and has been an excellent ambassador for the club. He's suffered a challenging period here with his knee injuries and, ultimately, Ian hasn't been able to play a regular run of games."
Agence France-Presse