Young Boys have become Celtic’s second Champions League opponents to sack their manager this season.
The Swiss champions have parted ways with Patrick Rahmen after just five months in charge.
The 55-year-old has presided over a terrible start to their title defence, with Young Boys bottom of the Swiss top flight having won just one of their opening nine matches.
Under-21 boss Joel Magnin has taken interim charge of the Swiss side, who make the trip to Parkhead on 22 January.
Croatian champions Dinamo Zagreb, who host Celtic on 10 December, also dismissed their manager early in the campaign.
Sergei Jankovic was sacked following the 9-2 defeat to Bayern Munich in their Champions League opener. Nenad Bjelica has returned for a second spell in charge following a short stint at the helm of Union Berlin.