Leverkusen sporting director Simon Rolfes said:, external “With Erik ten Hag, we have brought in an experienced coach with impressive success on the pitch.
“With three league titles and two domestic cup wins, he and Ajax dominated Dutch football from 2018 to 2022.
“And Erik demonstrated his quality as a coach with the ensuing success at Manchester United under difficult circumstances at times.”
Under former Liverpool midfielder Alonso, Leverkusen won a league and cup double in 2023-24.
They finished second in the Bundesliga this season, 13 points behind champions Bayern Munich.
Ten Hag, who will officially start his new role on 1 July, said Leverkusen are “one of the best clubs in Germany and also among the top clubs in Europe”.
He added: “I’ve come to Leverkusen to continue with the ambition shown in recent years. It’s an attractive challenge to set up something together in this period of change and develop an ambitious team.”