It's official: Alisson is the first goalkeeper to score a goal for Liverpool in the club's 129-year history.
Not only has he written himself into club folklore, he has potentially saved the Reds' season.
Had Liverpool not found a winner against West Brom, their Champions League hopes would have been all but over.
Having gone behind early on to Hal Robson-Kanu's pinpoint finish before equalising thanks to Mohamed Salah's whipped effort from the edge of the area, they had registered 25 shots without scoring again when Alisson came up for a corner deep into injury time.
Just as it looked as if all was lost, the Brazilian rose highest to meet Trent Alexander-Arnold's delivery and balloon a header into the back of the net. Cue absolutely frenzied celebrations and Jamie Carragher sounding like he'd just inhaled a massive amount of helium simultaneously.
Alisson's winner means that Liverpool are now only one point behind Chelsea in fourth and three behind Leicester in third. Chelsea and Leicester play each other on Tuesday evening, in a replay of the FA Cup final which the Foxes won for the first time at the weekend.
Asked about the goal after the match, Jurgen Klop told Sky Sports: "Pfft. Unbelievable. The header was unbelievable, I've never seen anything like that. It was insane, great technique.
"Nowadays you cannot be sure, is something wrong? So I turned around: 'Am I right, did we score?'
"It's great for the boys, it means a lot for us, we are still in the race, that's all we can do.
"Wednesday [against Burnley ], there will be the same fight and I have to say props to West Brom for their professionalism as they fought with all they had and made it really difficult for us, but we did it in the end."
The Liverpool boss also revealed a story he told Alisson and co about a similar incident from his playing days without the same happy ending. "I told the boys in the dressing room when I was a player a goalie scored a last-minute goal," he said. "It was the equaliser so we were celebrating like crazy.
"We came in the dressing room and then the club officials told us the name was wrong on the squad list so they took the points away from us.
"I checked [Alisson's name] so everything is alright. The game is our season in a nutshell, we do a lot of good stuff but we get hammered for the first mistake and we have to work like crazy.
"I told the boys nobody got over the top when it was 1-1 with the minutes going down and down.
"We had the best chances, but we kept playing football. It's really difficult against this side, how they defend and set up. But we needed Ali to sort it for us."
Those at the Hawthorns have testified to the hero's welcome that Alisson got when he returned to the dressing room, with the noise from his reception reverberating down the stadium corridors.
Some of his teammates could only react with stunned silence, however. Sharing his reaction on Instagram, Fabinho filmed himself shaking his head in disbelief before turning the camera on Alisson chatting away calmly to Adrian.
For Alisson, the goal held considerable personal significance. After the death of his father in February, he gave an insight into his emotions after the final whistle.
"I'm too emotional [over] these last months for everything that happened with me, with my family, but football is my life.
"I've played since [I can] remember as a human being with my father. I hope he was here to see it, but I'm sure that he sees it with God on his side and [he's] celebrating."