The Reds forward suffered a hamstring injury early in October while on international duty with Senegal and was not expected to return until after the next international break on 18 November.
Mane was named in Senegal's squad for their upcoming World Cup qualifiers against South Africa, much to the surprise of Jurgen Klopp, who was not expecting the wide attacker to return to action for at least six weeks.
However, the former Southampton star has surprised everyone by returning two weeks ahead of schedule. He was pictured training with the rest of the Liverpool squad on Thursday as they prepared for their clash against Slaven Bilic's side at the Olympic Stadium.
Mane's return will give Klopp much needed respite as they were facing a minor injury crisis, especially in midfield. Philippe Coutinho and Giorginio Wijnaldum are uncertain for the game against the Hammers, while Adam Lallana is yet to return to training from the thigh injury he picked up prior to the start of the campaign.
The Senegal international is unlikely to play a role against West Ham owing to his lengthy absence, and it remains to be seen if he will be allowed to join up with his national team for their game against South Africa.
The former Arsenal winger has been restricted to appearances off the bench, with his two starts coming in the Europa League and the EFL Cup so far. Klopp has been impressed with the England international and has indicated that he is ready to start his first league game.