Celtic face Cluj rematch and Lazio in Europa League group
The Scottish champions will also take on French side Rennes in Group E.
Celtic have been drawn to play Italian side Lazio in the Europa League group stage and face a reunion with CFR Cluj, who knocked them out of the Champions League.
The Italians are top seeds in the group and qualified for the competition after finishing eighth in Serie A last season.
Cluj, title winners in Romania last season, stunned Celtic in the Champions League third round by winning 4-3 in Glasgow and 5-4 on aggregate but were beaten 2-0 by Slavia Prague in the play-off for the elite competition.
Neil Lennon's side have also been drawn to face Rennes.
Rennes qualified as winners of last season's French cup, defeating Paris St Germain in the final on penalties after a 2-2 draw. The French side played Celtic as part of pre-season preparations, drawing 0-0 at Celtic Park.
The top two sides in the group will progress to the knockout stages.
Celtic dropped into the Europa League after being eliminated from the Champions League by CFR Cluj. They then defeated AIK Stockholm 6-1 on aggregate to reach the group stage.
Celtic's Europa League schedule
September 19 - Rennes (A)
October 3 - Cluj (H)
October 24 - Lazio (H)
November 7 - Lazio (A)
November 28 - Rennes (H)
December 12 - Cluj (A)