Dembele netted from the spot with 14 minutes left after Julian Korb had been sent off to earn Celtic a draw.
Celtic are still alive in the Champions League after Moussa Dembele's penalty allowed them to come away from their trip to Borussia Moenchengladbach with a 1-1 draw on Tuesday.
The Scottish champions seemed to be heading for elimination with two matches to spare in Group C after Lars Stindl gave the hosts the lead at Borussia-Park.
But Dembele netted from the spot with 14 minutes left after Julian Korb had been sent off to earn Brendan Rodgers' men a draw.
Celtic remain bottom of the section and are five points behind Manchester City in second place with a home clash against Barcelona and a trip to the Etihad Stadium still to come.
A last-16 spot is surely beyond them and catching a Gladbach side who are two points better off in the chase for a Europa League berth remains a big ask, but Celtic can be pleased at keeping their hopes alive.
"It was always going to be about learning for us this year," admitted Rodgers to BT Sport.
Celtic had been beaten 2-0 at home by Gladbach two weeks ago in Glasgow and Rodgers added: "To come here when they were clearly the better team two weeks ago, I felt we were the better side tonight and should have won the game.
"I'm very proud of the team tonight. I thought they were excellent."
The Hoops were missing Kolo Toure, Jozo Simunovic, Kieran Tierney and Leigh Griffiths due to injury but they could have gone in front in the first half, Scott Sinclair seeing a shot beat goalkeeper Yann Sommer but strike the post.
Gladbach had been the more dangerous team before that and the Bundesliga side went in front just after the half-hour mark.
Christoph Kramer's pass found Thorgan Hazard and his cutback was finished first-time by Stindl, who had also scored the opener at Celtic Park.
Celtic remained in the game, however, and won a penalty when Dembele was dragged down by Korb just at the point of shooting.
The defender was sent off by Portuguese referee Manuel De Sousa and Dembele -- who had missed from the spot in the 7-0 defeat to Barcelona in September -- netted from 12 yards.
Celtic might even have won it, too, but substitute Callum McGregor fired just wide at the end of a lovely late move.