The Brazil international will sign a five-and-a-half year deal at the Camp Nou and will have a release clause of €400m (£354.6m, $481.2m). According to the BBC, the La Liga leaders will pay a fee of around £142m to secure the former Inter Milan man's signature.
Following confirmation of the deal on Saturday [6 January], a statement on Barcelona's official website read, "FC Barcelona and Liverpool FC have reached an agreement for the transfer of Philippe Coutinho.
"The player will sign a contract for the remainder of the season and five more, and will have a buyout clause of €400m. In the next hours we will inform you of the details of the player's arrival and presentation."
Liverpool have confirmed that Coutinho's move to Barcelona is subject to a "medical and agreement of personal terms."
The 25-year-old was a transfer target for Barcelona boss Ernesto Valverde in the summer. The La Liga giants made multiple approaches in their attempts to sign the versatile star, who also handed in a transfer request in an attempt to force a move away from Anfield.
However, Liverpool decided against allowing Coutinho leave, only to now change their minds less than six months later.
Liverpool manager Jurgen Klopp has since revealed Coutinho was desperate to join Barcelona from the moment he learned of their interest in July 2017. The player even shared his desire to swap Anfield for the Camp Nou with the former Borussia Dortmund boss, the club's owners and even his teammates.
"It is with great reluctance that we – as a team and club – prepare to say farewell to a good friend, a wonderful person and a fantastic player in Philippe Coutinho," Klopp told Liverpool's official website.
"It is no secret that Philippe has wanted this move to happen since July, when Barcelona first made their interest known.
"Philippe was insistent with me, the owners and even his teammates this was a move he was desperate to make happen.
"Despite that, we managed to keep the player here beyond the summer window, hoping that we would be able to persuade him to stay and be part of what we are looking to do."
Klopp also went on to assure Liverpool supporters that the club did everything they could to retain Coutinho. However, the player had already made up his mind to join Barcelona as he felt a move to Spain would be best for his career.
"I can tell the Liverpool supporters that we, as a club, have done everything within our means to convince Philippe that remaining part of LFC was as attractive as moving to Spain, but he is 100 per cent certain his future – and that of his family – belongs at Barcelona. It is his dream and I am now convinced there is nothing left at our disposal to change his mind.
"Philippe has made a fantastic contribution to this club over his five years of service and as disappointed as we are he doesn't want to extend that, the relationship we have for him means with a heavy heart we wish him well.
"The player remained dedicated and committed to helping us win matches, producing good performances and training hard each day at Melwood after the summer window had closed, despite failing to convince us to allow him to leave during that period and that level of professionalism reflects positively on him.
"Of course, it is totally understandable that supporters will be disappointed; this is always the case when you have to say goodbye to someone special. But, as hard as it is sometimes to accept, it is part of life and part of football – individuals have their own dreams and their own goals and objectives in life.
"Players will come and players will go, that is football, but as a club we are big enough and strong enough to continue with our aggressive progression on the pitch, even when we lose an important player. We have never been in a better position in recent times, as a club, to react in the right way. We will use our size and strength to absorb moments like this and still move forward.
"I have been here long enough now to know in the history of Liverpool, key players have left before – but the club always goes on. You cannot transfer the heart and soul of Liverpool Football Club, although I am sure there are many clubs who would like to buy it.
"I have so much belief in the talent we have here already and even more faith, together with our owners, that we will make continued investment into the playing squad, which will allow more growth and more improvement.
"So as we bid farewell to Philippe, we continue on our path of progress and development as we work towards our common goal of bringing trophies back to Anfield."