Blind has signed a four-year deal with the Amsterdam club, having left Ajax for United in a £14 million deal ($18 million, 16 million euros) four years ago.
The 28-year-old Dutch international made 141 appearances for United, but his opportunities had become increasingly limited under manager Jose Mourinho and he played only seven Premier League matches for the Old Trafford club last season.
“I want to say how proud I am to be a part of the Manchester United family,” Blind wrote on Twitter.
“To play for the biggest club in the world with such a history meant a lot to me. I had 4 great years with 4 trophy’s (sic)!
“I want to thank you for all the love and support I received and still get. I will never forget some of the special games and moments, I will miss you ‘The Theatre of Dreams’! But now it’s time to go home.”
Although no transfer fee has been disclosed, British media reports said Blind, a defensive midfielder and full-back ,had rejoined Ajax in a deal worth an initial 16 million euros, with add-ons that could see the fee rise to 21 million euros.
Blind is the first senior player to leave United in this pre-season, although former England midfielder Michael Carrick had already announced his retirement prior to taking up a post with Mourinho’s backroom staff.
United wrote on their Twitter feed: “We can confirm @BlindDaley has left #MUFC to join Ajax. Thanks for everything, Daley, all the best for the future.”
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