The 26-year-old arrived on Merseyside in the early hours of Thursday morning after he immediately accepted Liverpool's proposal.
With a hectic fixture schedule arriving, Liverpool's hand was forced and they were left with no choice but to delve into the market.
Liverpool had pursued French international Aurelien Tchouameni earlier in the transfer window to strengthen their midfield however he opted for the current European Champions Real Madrid.
With less than 24 hours to go in the window, Liverpool decided on Arthur to come in as a stopgap signing to solve their midfield crisis.
There is no obligation to buy, but Juventus in their club statement has claimed there is an option to buy for £32M.
In Arthur's two years at Barcelona, he won both the league and the Spanish Super Cup after making 72 appearances.
Arthur made 31 appearances for Juventus last season but has not featured in their present campaign.
He has been capped 22 times for Brazil and won the Copa America alongside new teammates Roberto Firmino and Alisson Becker. He will hope that is not the last trophy he lifts with his fellow Brazilians.
How does Arthur play and how will he fit in?
He is only 5'7'' with a low centre of gravity and is an expert in retaining the ball and recycling possession. He is comfortable on the ball, technically gifted and extremely press resistant with high passing accuracy. These traits should help Jurgen Klopp's men better control games and add a calming presence when games start to get hectic by slowing it down when need be.
He can play as both a number six and number eight, meaning that he is able to fill in for the injured Thiago in the left-centre midfield role as well as cover for Fabinho as a deep-lying playmaker. He is comfortable receiving the ball under pressure and enjoys receiving the ball on the half-turn. Very much like the Red's other midfield maestro, Thiago.
He has averaged more touches per 90 than any other Juventus player over the last 2 seasons and ranks top in terms of passes, pass success and ranked 2nd in passes into the final third.
He also offers plenty out of possession with statistics showing he has won possession in the middle third of the pitch at a higher rate than any other Juventus player over the last 2 seasons (Sky Sports).
Arthur is a player who can dictate the tempo and with his superb passing range and technical ability he could ease the burden on Thiago.
He also has the backing of arguably the best player of all time- Lionel Messi. Speaking to Spanish outlet "Tot Costa" in 2018 he said:
"Those who came are very good. Arthur I didn't know that much about but he seems similar to Xavi, he's very safe and trustworthy. He has the La Masia style".
"Playing short passes, without losing the ball, and he grasped it quickly, the dynamic of the team".
Arthur's first interview
The Red's new signing certainly seems excited about joining the English Giants. Speaking to the club's official website he said:
"I'm really, really happy to be here wearing this great shirt with this famous badge that represents so much in world football, it's a dream".
"We talked a lot, and our ideas and visions were a good fit so I'm sure it was the right choice. I'm really happy and highly motivated to continue living my dream on the pitch and giving my all in a Liverpool shirt".
"Liverpool have a wonderful history in football. I've played against Liverpool, I know what it feels like to be in the stadium with the fans behind them".
"I was with the opposition and now I'm on the right side so I'm really excited. It's a massive club with a great manager, great players. As I said before it's a dream to be here".