Here's Giggs' open letter to fans, in which he wrote about, "a chapter filled with many emotions," and reflected on a playing career that brought 34 major trophies.
And here's the best of the Twitter reaction to Giggs' retirement, and his new role alongside Van Gaal.
Ryan Giggs won a Premier League title on average once every 48.6 games during his top flight Man Utd career. Unreal! pic.twitter.com/R06HTQKQAp— Squawka Football (@Squawka) May 19, 2014
Giggs retires. "Today is a new chapter filled with many emotions - immense pride, sadness, but most of all excitement" #MUFC— Daniel Taylor (@DTguardian) May 19, 2014
With Ryan Giggs' retirement, that's officially the end of the Manchester United Class of '92. A new era begins. pic.twitter.com/4itFy3ODQR— Football__Tweet (@Football__Tweet) May 19, 2014
Ryan Giggs has retired from playing so I'm not 100% convinced there's gonna be football next season.— Paul (@UtdRantcast) May 19, 2014
Some day for retirements. First Jonny Wilkinson and then Ryan Giggs...— Mark Ogden (@MOgdenTelegraph) May 19, 2014
Giggs: "I'm thrilled to have the chance to serve as assistant manager. Louis van Gaal is a world-class coach and I know I will learn a lot."— Rob Dawson (@RobDawsonMEN) May 19, 2014
12 months to the day since Fergie's last game at Man Utd. In one year - an Everton influx, then a Dutch one. Giggs the last man standing.— Paul Hayward (@_PaulHayward) May 19, 2014