Dong Fangzhuo's United contract has been cancelled by mutual consent.
The 23-year-old striker became the first ever Chinese player at Old Trafford when he joined from hometown club Dalian Shide in January 2004. He initially spent two years on loan at Royal Antwerp until he was eligible to play in England, and scored 35 goals in 61 games during his time in Belgium.
Dong pulled on the red shirt for the first time in a friendly against Hong Kong XI in July 2005 and scored in the 2-0 win. The following summer he got the winning goal in a 1-0 win over Kaizer Chiefs during the pre-season tour of South Africa.
Dong finally made his competitive debut for the senior side against Chelsea in May 2007, but his struggle to break into Sir Alex Ferguson's squad continued last season.
The forward enjoyed some success in the Reserves, scoring four goals in a three-game purple patch in November.
He also played twice for the senior side in 2007/08, in September's Carling Cup defeat to Coventry and as a substitute in the 1-1 Champions League draw in Rome, before a knee injury ended his season early.
In this summer's Olympics in his homeland he scored a late equaliser for China against New Zealand, but could not prevent his country exiting the tournament at the first stage.