Giggs, who started playing professionally in 1990, finishes his career having won 34 major trophies.
Here, Sports Mole picks out a selection of tweets in praise of English football's most decorated player.
Former England striker Gary Lineker: "Ryan Giggs has retired from playing. One of the greats of his time. A very long time! Wonderful player, astonishing athlete and a winner."
Ryan Giggs retires today....so many gold medals he puts B.A. Baracus to shame! No player adapted their game as well & as effective as Giggsy— Rio Ferdinand (@rioferdy5) May 19, 2014
Former Manchester United and Stoke City defender Danny Higginbotham: "Amongst all the news from OT today it seems as though not much has been made of Ryan Giggs retiring. He has to be best ever united player."
Manchester United striker Wayne Rooney: "Congratulations also to Ryan Giggs on a special career and becoming assistant manager, I'm sure he will do a great job."
Former Manchester United teammate Gary Neville: "Ryan Giggs a truly great footballer and Career. His title haul will never be beaten in England.."