The Welshman retires with 963 appearances to his name, having racked up an incredible 13 Premier League titles, four FA Cups and two UEFA Champions League crowns to become by far the club's most decorated player.
In an open letter to the club's fans, he said: "Today is a fantastic day for Manchester United. Louis van Gaal is a great appointment and let me begin by telling you how delighted I am to be working with someone of his calibre.
"I would also like to take this opportunity to announce my retirement from professional football and embark upon a new and exciting chapter in my life, as assistant manager of Manchester United.
"I am immensely proud, honoured and fortunate to have represented the biggest club in the world 963 times and Wales 64 times."
Giggs made his debut as a 17-year-old flying winger against Everton in March 1991 and lifted his first silverware in the shape of the 1991 UEFA Super Cup - coming on as a substitute in the 1-0 win over Red Star Belgrade.
He was immediately thrust into the United first team by Alex Ferguson - becoming the first of the legendary 'Class of 1992' to break into the side.
As the likes of Paul Scholes, David Beckham, Nicky Butt and the Neville brothers followed him into the team, United began to dominate English football, winning seven of the first nine Premier League trophies.
Perhaps Giggs' most memorable contribution came on April 14, 1999 with United and Arsenal locked at 1-1 in extra-time of their FA Cup semi-final replay.
Giggs picked up the ball in midfield before slaloming his way through a series of defenders and slamming the ball into the roof of the net.
An historic treble of league, Cup and Champions League was secured that season - the only such feat ever achieved by an English club.
As the years drew on, Giggs remained as his previous academy colleagues left the club, and his role changed too - becoming a cultured playmaker in the centre of the park.
He also managed the club on an interim basis this season after David Moyes' sacking - highlighting the esteem and regard he held at Old Trafford.
His final appearance for United came as a substitute in their 3-1 win over Hull City, while his last goal was scored the previous season against QPR in a 2-0 triumph.
