Valencia signs new Man United contract
The 25-year-old has made a big impact since joining from Wigan Athletic in 2009, although he was sidelined for much of last season with a broken ankle.
"Antonio has made a fantastic contribution since his arrival. His speed, crossing ability and versatility have been a big asset for us," manager Sir Alex Ferguson told United's website.
"He has a quiet, unassuming way of going about his business, which is underlined by great strength of character - as his recovery from such a bad injury last season proves."
Valencia has made 69 appearances for United, scoring 10 goals.