"You run out of words to describe Ryan Giggs. He is a marvellous player and a wonderful man," manager Alex Ferguson was quoted as saying by the Red Devils' official website.
"To have the desire and the ability to play at the top level in such a physically demanding position at his age requires a special person.
"He is still turning in man of the match performances and his experience is so vital for the younger players in the squad."
The one-club man, who kicked off his professional career in 1990 and made his senior debut a year later, has achieved a record of 862 club appearances so far.
Giggs won 11 Premier League titles, four FA Cups, Three League Cups, two Champions Leagues, one Super Cup, an International Cup and a Club World Cup. He scored 158 goals for United.
"All I've ever wanted to do is play for United and I've been lucky enough to do that for 20 years," 37-year-old Giggs said.
"It's great to know I'm still contributing to the team's success and I feel I've got a lot to offer on and off the pitch.
"This is an exciting time to be involved with so many good young players coming through."