Liverpool 2 Ludogorets 1: Gerrard spot on for hosts
Gerrard sent debutant goalkeeper Milan Borjan the wrong way from the spot in added time to earn a win amid a chaotic and stunning finish to the game.
It appeared that the Bulgarians, in the group stages of the competition for the first time, had stolen a remarkable point when Dani Abalo coolly rounded Simon Mignolet and slotted home just before the 90-minute mark.
But Borjan, only signed on Friday due to the visitors' two main goalkeepers being ruled out, made a critical error when bringing down Javi Manquillo in the area.
And Gerrard made no mistake, adding to Mario Balotelli's 82nd-minute strike - his first for the club - to steal the points in Group B on the night Liverpool returned to this tournament after a five-year exile.
Canadian Borjan - who has not played regular club football in over a year - took his place between the posts, having been signed following an unsuccessful spell with Sivasspor in Turkey.
His inclusion came as first-choice Vladislav Stoyanov - whose sending off infamously paved the way for defender Cosmin Moti to save two penalties in the qualifying penalty shoot-out win over Steaua Bucharest - served his suspension, while deputy Ivan Cvorovic missed out with a shoulder injury.
Canada's number one was not tested during the early exchanges, though, as Ludogorets more than held their own.
Borjan passed his first test when showing strong hands to keep out Adam Lallana's deflected effort following good work from Balotelli, but it was the visitors who enjoyed the better of the opening half.
Liverpool were restricted mainly to efforts from distance, the best of which came when Balotelli drew a smart stop from Borjan.
A good move finally brought their first significant opening in the 38th minute, Jordan Henderson sliding a pass to Lallana - whose goal-bound effort was blocked.
Liverpool emerged from the break with purpose and came agonisingly close to taking the lead when Manquillo poked a shot just over after receiving a fine cross-field pass from Henderson.
Ludogorets were quick to offer a reminder of their threat, however, with Junior Caicara stinging the hands of Mignolet.
Brendan Rodgers' side were still the more dynamic, although further moments of alarm came when Roman Bezjak narrowly shot over.
The game was suddenly end to end, with Borjan turning Gerrard's powerful header over the crossbar.
Bezjak was then denied by the woodwork following a wonderful ball from Marcelinho.
There were further nervy moments for Liverpool, including Alberto Moreno making a wonderful last-ditch challenge to deny the impressive Marcelinho, until Balotelli finally broke the deadlock with eight minutes left.
The Italian brought the ball down inside the area before turning and slotting beyond Borjan with a delicate volley.
It proved to be only the first act in the late drama, though, as Abalo then capitalised on a lapse in concentration to level on the stroke of full-time - producing a composed finish after rounding Mignolet.
Yet that error paled in comparison to the dreadful moment from Borjan, who miscontrolled a back-pass and then brought down the marauding Manquillo - allowing Gerrard to once again step up and be the hero on a big European night at Anfield.