Nagelsmann has signed a contract until 2023 at the Red Bull Arena, after taking advantage of a release clause in his Hoffenheim contract to allow him to move on at the end of the upcoming campaign.
Following the departure of Ralph Hasenhüttl, Leipzig are yet to confirm a coach for the 2018/19 season, but the club issued a statement that an announcement will be made in a press conference prior to the start of pre-season training.
OFFICIAL: Julian #Nagelsmann will become RB Leipzig head coach from the 2019/20 season.— RB Leipzig English (@RBLeipzig_EN) 21 June 2018
The 30-year-old joins from @achtzehn99_en and has agreed a contract with #DieRotenBullen until 2023. #Nagelsmann2019 pic.twitter.com/DVRrvBHR4c
"It was important to me to do this early to establish clarity in my relationships," said Nagelsmann. "I owe it to the club and its employees – as well as the team and the fans – to ensure that this historic upcoming season, in which we will play Champions League football for the first time, does not become dominated by speculation about my future.
"Now that everyone is aware of how things stand, we can concentrate on the tough tests in a professional fashion. Everyone is aware that I will give everything for TSG until the very last second of my time here and will do everything to achieve our ambitious aims."
Watch: Nagelsmann is Germany's coaching prodigy!
"We knew about the release clause in the contract, something hardly uncommon in the world of professional football," said Alexander Rosen, Hoffenheim sporting director. "It speaks well of Julian's character that he has put his cards on the table now in public and ensured clarity."
The youngest coach in Bundesliga history, Nagelsmann guided Hoffenheim to a top-four finish in each of the last two seasons, missing out on a UEFA Champions League place in 2017/18 after a play-off with Liverpool, but securing an automatic berth for the coming year.
Nagelsmann has been at Hoffenheim in a coaching capacity for over nine years – since ending his playing career early due to injuries – and rescued the first team from relegation after taking over from Huub Stevens in February 2015, before leading a vibrant, young side to successive top-four finishes.