The 40 year old is the most decorated player in the English game , having won 13 league titles, four FA Cups and two Champions Leagues, among 34 trophies.
He said: "Today is a new chapter filled with many emotions - immense pride, sadness, but most of all, excitement towards the future.
"My dream was always to play for Manchester United, and although it saddens me to know I won't be pulling on a United jersey again as a player, I have been lucky enough to have fulfilled that dream playing with some of the best players in the world, working under an incredible manager in Sir Alex Ferguson, and most of all, playing for the greatest fans in world football," said the Welshman.
"I am immensely proud, honoured and fortunate to have represented the biggest club in the world 963 times and Wales 64 times.
"United fans I hope will share and echo my belief that the club, the management and owners, are doing everything they can to return this great club to where it belongs, and I hope to be there every step of the way."
"What he has achieved will never be equalled in the English game."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball