The 24-year-old joins the Magpies from the Major League Soccer side for an undisclosed fee, penning a five-and-a-half-year deal which will keep him at St. James’ Park until June 2024.
Paraguayan international Almirón – who has 13 caps for his country – netted 13 goals and 13 assists to help Atlanta win the 2018 MLS Cup.
He began his career with Cerro Porteño in his homeland before moving to Argentinian Primera Divisíon outfit Club Atlético Lanús in the summer of 2015.
After 16 months with the Granate, Ascunción-born Almirón joined Atlanta in December 2016 and was named MLS Newcomer of the Year at the end of his first campaign at the Mercedes-Benz Stadium.
Almirón has twice featured for the MLS All-Star team, and was selected in the MLS Best XI at the end of both of his seasons with the Georgia-based club.
He will wear the squad number 24 for the Magpies.
"I’m very happy and eager to start and to meet my new team mates," Almirón told NUFC TV. "The league is very competitive, this is a historic club, and Rafa Benitez himself were the main reasons why I am here now.
"I think it is a great responsibility, something beautiful for me, and I will try to offer the best I can to repay the trust the club put in me."
United manager Rafa Benítez added: "We were following Miguel Almirón for a while, and we saw a player with some pace in attack, who can play behind the striker. We have someone who can score goals and give assists.
"We know that MLS is a different challenge to the Premier League but he has the potential to do what we are expecting, and what we need.
"From talking to the lad, you can tell that he is really focussed and wants to do well. He wants to be successful and he wants to help the team, to score goals and give assists if it is possible.
"His impact in MLS has been really good - he's been one of the best players this year - and hopefully he can give us more competition and more quality in the final third.
"I am pleased that the hard work behind the scenes has ended positively and I thank everyone for their efforts."
