The 33-year-old has played for three of the four Welsh regions – Scarlets, Blues and Ospreys – and is currently at his second club in France, Racing 92. He previously played for Bayonne.
During his international career with Wales h won three Six Nations titles and two Grand Slams. He was also at the heart of the side that reached the semi-finals of the 2011 Rugby World Cup.
“Playing for Wales has been such a huge part of my adult life and this is a chance for me to say ‘thank you’ to everyone – from family and friends, the coaches and management of the Welsh Rugby Union, all of the great players that I have been fortunate enough to play with and against and, of course, the fantastic Welsh fans for their great support,” Phillips said in a statement.
“It was always a dream of mine to play for Wales, it meant everything to me, and it’s an amazing feeling to represent your country. For me it was a privilege.”
He made his debut for Wales against Romania in Wrexham in 2003, but missed out on a place in the World Cup later that year. He emerged from the shadow of former Scarlets team mate Dwyane Peel to become Wales’ leading scrum-half under Warren Gatland.
His last match for Wales was the World Cup warm-up defeat by Ireland at the Millennium Stadium on 8 August this year. He returned to the World Cup squad when Rhys Webb was injured, but didn’t get another game as Gatland stuck with Gareth Davies and Lloyd Williams.
He established himself as the leading scrum half in the northern hemisphere o two tours with the Lions. He played in all three Tests against the Springboks in 2009, ending up at centre in the final Test triumph over the then World champions in Johannesburg, and played in the two wins over the Wallabies four years later.
He remains on the books at Racing 92 and hopes to link up with New Zealand legend Dan Carter in the next few weeks.