A stunning second-half resurgence from Besiktas saw them recover from three goals down to earn a 3-3 draw that prevented Benfica from qualifying for the Champions League knockout stages and boosted their own hopes of progressing.
Goals from Goncalo Guedes, Nelson Semedo and Ljubomir Fejsa inside the opening 31 minutes looked like sending the Portuguese champions on their way into the last 16.
However, Cenk Tosun, Ricardo Quaresma and Vincent Aboubakar struck after the restart - the latter netting with one minute remaining - to claim a point in what was a memorable comeback in Istanbul.
Benfica headed into the crunch clash at the Besiktas Arena well aware that three points would be enough to qualify from Group B, but the draw means that the sides occupy the top two spots in the pool, potentially temporarily as they await the result of Napoli's game with Dynamo Kiev later on Wednesday.
The first warning sign of what was to come for Besiktas in a torrid first half arrived with less than three minutes gone when Eliseu found space to shoot on the edge of the box and his effort hit the outside of the post.
The hosts thought they had taken the lead two minutes later, as Aboubakar tapped home a rebound only to see the assistant referee cut his celebrations short with an offside flag.
It was Benfica, though, who broke the deadlock after 10 minutes. Guedes was calm under pressure after being put through on goal by Eduardo Salvio and he rounded goalkeeper Fabricio Ramirez before slotting in from close range.
Semedo compounded Besiktas' misery by adding a second 15 minutes later when he produced a stunning strike from distance, unleashing a dipping shot that struck the crossbar and landed in.
And it was 3-0 just after the half-hour mark, with Fejsa finally converting after Benfica had hit the woodwork three times in as many seconds. First, Kostas Mitroglou was denied by the bar with a pair of headers, then Salvio nodded against the post before Fejsa eventually tapped home to leave the hosts shell-shocked.
Salvio saw a low shot well saved early in the second half before he slid in Mitroglou, who slotted wide despite being clean through on goal.
Senol Gunes' team were given a glimmer of hope thanks to a wonderful 58th-minute strike from Tosun, who produced an acrobatic volley into the far corner from Andreas Beck's cross.
Victor Lindelof gifted the hosts a second seven minutes later when he handled inside the box and Quaresma converted the resulting spot-kick off the right-hand post to set up a grandstand finish that ended with Aboubakar hauling the sides level.
It was heartbreak for Benfica as Aboubakar, on loan from their rivals Porto, scrambled home from close range following Quaresma's rabona cross to complete the comeback.