The 25-year-old damaged his anterior cruciate ligament in Chelsea’s 4-0 Champions League win over Juventus on November 23.
The Blues had hoped Chilwell could return to action without surgery, but the former Leicester star will now undergo the ligament repair operation.
Chelsea could look to the transfer market to bolster their Premier League title bid in January, with Everton’s Lucas Digne strongly mooted as an option for the Blues.
“After a knee injury in the match against Juventus the Chelsea medical department, in collaboration with their knee specialist, took the decision to attempt a conservative rehab approach,” Chelsea confirmed in a club statement.
“Unfortunately Ben was unable to progress and so collectively the decision has been taken to proceed this week with a surgical repair.”
Marcos Alonso is Chelsea’s sole frontline left wing-back in Chilwell’s absence, leaving boss Thomas Tuchel having to shuffle his resources for alternatives.
Callum Hudson-Odoi, Saul Niguez and Christian Pulisic have deputised without yet appearing fully comfortable in the role.
The Blues could also look at recalling either Ian Maatsen or Emerson Palmieri from their loan stints.
Maatsen has impressed at Coventry in the Championship, while Emerson has been a regular in his temporary stint at Lyon.
Chelsea hit back to form with a battling 3-1 win at Aston Villa on Boxing Day, with Romelu Lukaku stepping off the bench to turn the game in the visitors’ favour.
The Belgium hitman nodded home a fine goal to signal his return to sharpness after an ankle injury and then Covid-19 isolation, and has now insisted he can fill any role required by Blues boss Tuchel.
“We had a couple of conversations about whatever he wanted from me,” Lukaku told ESPN Brazil. “And I told him I’m multidimensional.
“So it’s about having a bit of clarity about how he wants to use me.
“And whatever he wants from me I think I can do whatever aspect he wants from the game, I can run in behind, I can press, I can hold the ball up.
“So I think throughout the years these are qualities I added to my game.
“I just wanted the opportunity, I’m happy that I got it and now I just want to move the team forward.”
Chelsea host Brighton in Wednesday’s Premier League clash hoping to build on the win at Villa, but they are again sweating on a host of injury and Covid-related issues.
Ruben Loftus-Cheek will be a doubt with a foot injury, while Timo Werner and Kai Havertz may be able to return after Covid-19 isolation.
Thiago Silva picked up a thigh concern at Villa and N’Golo Kante suffered a knee issue, with both further doubts to face Graham Potter’s men.