Scott Sinclair boosted Celtic's chances of qualifying for the next round of the Europa League with the only goal in a 1-0 win at Rosenborg that ended the Norwegian side's hopes of progressing.
Sinclair headed in an excellent right-wing cross from James Forrest shortly before half-time to earn a crucial Group B victory at Lerkendal Stadium on Thursday.
Celtic host Salzburg - who have already qualified as the pool's winners - on matchday six next month knowing a draw is enough to send the Scottish champions into the knockout stages.
Tom Rogic and Odsonne Edouard missed Celtic's best chances in a lively opening from Brendan Rodgers' side, who took the lead in the 42nd minute.
Forrest, who scored five goals in two games for Scotland over the international break, brilliantly beat Tore Reginiussen and delivered a wonderful deep cross for Sinclair to head in.
Rosenborg appeared to have an eye on Sunday's cup final against Stromsgodset, with Rini Coolen's side lacking intensity during an attempted second-half fightback.
Edouard saw an effort blocked by team-mate Ryan Christie as Celtic sought a clinching second, but Samuel Adegbenro missed a good headed chance from a Rosenborg corner at the other end.
And although the hosts - yet to earn a point in Group B - mounted some late pressure, Celtic held on for their first away win in the Europa League since the competition was rebranded for the 2009-10 season.
Salzburg's 1-0 home win against RB Leipzig, secured thanks to Fredrik Gulbrandsen's second-half goal, means Celtic only need to avoid defeat to qualify when the Austrian side head to Glasgow on December 13.