Former Dutch international and Ajax and Barcelona defender De Boer, 48, worked in the Premier League as manager of Crystal Palace but lasted only four league games.
However it was his record of developing young players at Ajax that impressed the MLS club.
“Frank de Boer has a distinguished background, both as manager and player, and we’re ecstatic to welcome him to our club,” Atlanta United president Darren Eales said in a statement.
“When we began our search, we were determined to find someone who fit all of our criteria. In addition to meeting our club’s core values, Frank’s philosophical views for how to play unequivocally align with ours.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
“He also has a proven track record of developing youth players, with many of them going on to star for top European teams. Finally, his multilingual capabilities, including Spanish and English, ensure a smooth transition in the leadership of our club."
One of his country's finest defenders, De Boer featured in two World Cups and three European Championships for the Netherlands.
His managerial career has been spotty. He enjoyed great success with Ajax, where he won the Eredivisie four times in five-and-a-half years.
His brief stints at Inter Milan and Crystal Palace both ended with him being fired.
Atlanta United, only in their second year of existence, won the MLS Cup by defeating Portland 2-0 this month.
(Reporting by Gene Cherry in Raleigh, North Carolina; editing by Clare Fallon)
