Diallo has joined the Red Devils on a four-and-a-half-year contract that could be worth up to £37m, with the deal having been agreed with the Serie A side back in October.
The 18-year-old Ivorian winger made two appearances for Atalanta’s senior side in the first half of the 2020/2021 season, including a Champions League debut against Midtjylland in December.
“Dear Atalanta, the moment to say goodbye has arrived,” Diallo said in a video posted on Twitter.
“It has been six extraordinary years, six years of growth, six years of challenges. But most importantly, six years of happiness and love.
“Here, I have become a man; you have given me everything I ever wanted, and I am more than proud to have played for Atalanta.
“You will forever have a special place in my heart. Wherever I go, you will always be with me for now and forever. Forza Atalanta!”
Speaking of his arrival, United manager Ole Gunnar Solskjaer said: “As a club, we have followed Amad for a number of years and having watched him myself, I believe he is one of the most exciting young prospects in the game.
“Manchester United has such a proud history of developing young players and everything is in place to enable Amad to reach his potential here.
“It will take time for him to adapt but his speed, vision and fantastic dribbling ability will stand him in good stead to make the transition. He is a player with all of the raw attributes that are needed to be an important player for Manchester United in the years to come.”
