French World Cup winning midfielder Paul has returned to Serie A side Juventus on a free transfer, the Italian giants announced on their website on Monday.

The 29-year-old enjoyed a highly successful first spell at Juventus (2012-16) before Manchester United swooped to sign him for a then record 105 million euros ($106 million).

"Paul is back in Turin," Juventus said on their website below a photo of a grinning Pogba in a Juventus shirt.

"He left as a boy and returns as a man and a champion.

"But there is one thing that has not changed -- the desire to write unforgettable pages of club history together once more.

"Pogba is back and we couldn't be happier."

Pogba underwent his medical over the weekend and has signed a four year deal which will earn him a reported eight million euros ($8.12 million) a season plus a potential two million euros in bonuses.

"Juventus Football Club S.p.A. announces that it has signed a contract of employment with the player Paul Pogba," read the statement.

"Juventus will incur ancillary costs of EUR 2.5 million, to be paid within 31 August 2022.

"Juventus and the player have signed a contract of employment until 30 June 2026."

He rejoins Juve after his contract with Manchester United expired at the end of last month, marking the end of a largely disappointing six years back in England.

Dysfunctional United are further away from the top of English football than when he joined. They have not won a Premier League title in nine years.

The 2017 Europa League and the same season's League Cup are a poor haul for Pogba at one of the world's biggest clubs, especially as they both came under Jose Mourinho, a period when Pogba has said he first suffered from depression.

Pogba is expected to inherit the number 10 jersey  from Paulo Dybala, who could join Juve's fiercest rivals Inter Milan after the Argentina forward was let go by the Turin giants.

Pogba wore that jersey in his final season at Juve, joining such iconic playmakers as Roberto Baggio, Alessandro del Piero, Michele Platini and Liam Brady.

He had moved to Juve from United four years previously while still a teenager and made a huge impression in a slick midfield featuring the likes of Andrea Pirlo and Arturo Vidal.

Pogba blossomed when coach Massimiliano Allegri replaced Antonio Conte in 2014. The Frenchman drove a powerful team to the following year's Champions league final, losing to Barcelona.

He won the Serie A title in each of his four seasons at the Old Lady of Italian football and retained his affection for Juve. He was linked with a return on several occasions during his time at United.

Allegri will be hoping that Pogba can help Juve return to their former glories after they finished fourth last season, 16 points behind champions AC Milan.

Pogba is Juve's second notable signing in recent days. The club secured the signature of veteran Argentina winger Angel Di Maria after he was released by French champions Paris Saint-Germain.