Liverpool have signed Keita but he won't pitch up on Merseyside for another 12 months.
The Reds have agreed a fee of around £60m with RB Leipzig for the Guinea midfielder.
However he'll spend the rest of the season with the German club, before switching to the Premier League in 2018.
Keita said: “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.
“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.”
Keita only joined Leipzig from sister club Red Bull Salzburg a year ago.
And he made a huge impression in his debut Bundesliga season, scoring eight goals in 31 league appearances as the promoted side claimed a shock second-place finish.
Keita will become Liverpool's record purchase, with the fee of around £60m dwarfing the £39m club record that was set earlier this summer when Mohamed Salah joined from Roma.
But the deal for the Leipzig star could be blown out of the water if Liverpool succeed in landing Thomas Lemar from Monaco.
Two bids have been rejected for the Monaco star, but Jurgen Klopp is willing to spend more than £70m to get the France international.
