Last week, the club announced that Marouane Fellaini had extended his stay at Old Trafford by a further 12 months, and on Tuesday Valencia followed suit.
Initially signed as a winger, Valencia has established himself as United's first-choice right-back, making 23 starts across all competitions under Jose Mourinho this season.
His major honours at Old Trafford include two Premier League titles, in 2011 and 2013, as well as the 2010 League Cup and last year's FA Cup triumph.
Mourinho has always been a fan of Valencia's ability and admitted earlier this season that he tried to sign him while in charge of Real Madrid.
“I tried to sign Antonio a number of years ago, when I was at Madrid," he said.
“Even though he was not playing right-back at the time, I thought he could be phenomenal in that position. As it was, United told me 'no chance!'
“I am not surprised by his form this season. He has been clean of injuries, save for an operation on his arm which did not keep him out for long, and I have also been able to keep him fresh by resting him in certain Europa League games.
"I think he is the right-back to give us the maximum we can in terms of our attacking football.”