The Reds and England skipper picked up a hamstring strain in Saturday's 4-1 win over West Ham and will miss vital clashes with Tottenham, Manchester City and Chelsea.
Gerrard limped out of the action on 56 minutes to be replaced by Lucas Leiva and underwent a scan on Monday which confirmed the extent of the injury.
The 33-year-old's absence comes at a key time for the Reds, who sit second in the Premier League and face Tottenham, Manchester City and Chelsea in their next four games.
The news is also a fresh blow to Brendan Rodgers, who is already without in-form striker Daniel Sturridge until well into the New Year because of an ankle problem.
Gerrard has appeared in all 15 of Liverpool's Premier League matches so far this season, notching three goals and six assists - the joint-highest in the division alongside Arsenal's Mesut Ozil.