The world’s strongest beer is 67.5% alcohol by volume.

An excerpt from the article 20 facts about beer

It is called Brewmeister–Snake Venom; it comes from Scotland and its producer recommends drinking the beverage in 35ml glasses. Other very strong beer varieties include BrewDog 578, Brewmeister–Armageddon, Brouwerij‘t Koelschip–Start the Future, and Obilix.