The Dutchman replaces Quique Setien after he was axed following the humiliating 8-2 defeat to Bayern Munich in the Champions League and is set to give a press conference later on Wednesday (19.08.20).
Koeman spent six years as a player at the Nou Camp in Johan Cruyff's 'Dream Team' and scored the winning goal in the European Cup final in 1992. He has left his role as head coach of the Netherlands national team to take up the position at Barca and has signed a two-year contract.
Speaking before his appointment was confirmed, club president Josep Maria Bartomeu told Barcelona's website: "We already know how he thinks and his philosophy. We bet on him. He was the first one we called in January.
"It's a dream for him. As he was in Johan's 'Dream Team', he knows Barca and how we understand football."
Bartomeu also added that Lionel Messi will be a key figure during Koeman's reign, despite speculation linking him with a move away after the loss to Bayern.
He said: "I have spoken with Koeman and the pillar of our project is Messi. He has a contract until 2021.
"I speak a lot with Leo and more regularly with his father.
"He is number one in the world. There is no doubt that in Koeman's new project you can count on Messi."
The president added that Koeman will decide the fate of Philippe Coutinho, who has spent the season on loan at Bayern Munich and scored twice in the Champions League clash.
Bartomeu said: "The head coach will make the decision. If he wants him to continue, next year he will play with us."