The highly-rated 18-year-old moves to France after an impressive spell on loan in Spain with La Liga basement club Real Valladolid, where he made 12 top-flight appearances.
It was reported earlier this month that Man City had verbally agreed to sign Bah from his parent club AIK Freetong in his native Sierra Leone, but the Citizens were accused of "appearing to advise" the youngster by Real Valladolid.
The Spanish club, who exercised a purchase option to sign Bah on a permanent transfer earlier this month, informed their legal department to "initiate disciplinary action" after claiming that Bah was in breach of contract for failing to turn up for training.
Despite the controversy, Man City have now confirmed that Bah has "completed his registration" with the club, while Lens have officially unveiled the defender as their latest signing on loan from the Premier League champions.
Lens confirm Juma Bah loan signing from Man City
A statement from Lens read: "From the "Lion Mountain" to the Artois slag heaps! An athletic player (1.95m), engaged in duels and dominant in the air, Juma Bah (18 years old) completes the blood and gold defensive sector from Manchester City FC. The talented Sierra Leonean defender joins Artois on loan until June 2025."
The Ligue 1 club added: "A symbol of his progress and potential, Juma Bah has been scrutinized by several European giants in recent weeks. He then signed with the English club Manchester City before being loaned to RC Lens."
Meanwhile, Man City have released a short statement which read: "Juma Bah has joined RC Lens on loan until the end of the season, having completed his registration with Manchester City.
"The 18-year old central defender moves to Ligue 1 after a spell in Spain with Real Valladolid.
"Born and raised in Sierra Leone, the teenager received a senior international call-up in May 2024, joining the squad for their 2026 FIFA World Cup qualification matches against Djibouti and Burkina Faso.
"Everyone at Manchester City wishes Juma the very best of luck during his spell."
Man City'a decision to loan Bah to Lens comes after they completed the signing of Abdukodir Khusanov from the French club last week for a reported €40m (£33.5m).
McFarlane joins Man City from NYCFC
Meanwhile, Man City's sister club New York City FC have announced that their 18-year-old left-back Christian McFarlane has been sold to the Citizens.
McFarlane, who had been with New York City since the age of 11 and represented them at every age group, becomes the club's first home-grown player to join a Premier League side.
"I want to give all my thanks to David Lee (Sporting Director), Sam Pugsley (NYCFC's Vice President of Sporting Operations) and everyone at the club for always advocating for me," McFarlane told the club's official website. "Their support has meant so much, and I truly appreciate everything they've done for me and my career.
"Making a move to Manchester City is a huge step, and I'm grateful to be part of the City Football Group. Having that connection is so important, and it shows young players out there that if you have the right mindset and work hard, opportunities like this are possible. It's a dream come true, and I'm excited for what's ahead."
McFarlane made his first-team debut for NYCFC last year and went onto play a total of 13 times for the senior side, including eight MLS appearances in 2024.
New York City FC have confirmed that they will receive a sell-on percentage if McFarlane is sold by Man City in the future, while it remains unknown as to whether the left-back will be immediately integrated into Pep Guardiola's first-team plans.
Written by
Oliver Thomas