The Premier League outfit have confirmed that the Guinea international will move to Anfield on July 1, 2018 after reaching an agreement with RB Leipzig.
The Reds have been trying to get Keita through the door all summer, and now they have finally got their man in what is believed to be a club-record deal worth more than £48m.
Even though the midfielder will not join up with his new club until next year, he will be keeping a close eye on how Jurgen Klopp's team perform this season.
"I am delighted that an agreement has been reached which will allow me to join Liverpool Football Club next summer, when I will become part of a project that excites me greatly," Keita told the club's official website.
"My commitment to RBL remains absolute for the remainder of my time at the club. I have given my all every time I have worn the shirt - that will be the case until the final whistle, in my final appearance.
"Having my future resolved means I can now focus on helping RBL achieve great things this season. Until I join my new club, next summer, I will remain an interested supporter from a distance."
The 22-year-old scored eight goals in 31 Bundesliga appearances last season.