Which German beer purity law must beer sold at Oktoberfest follow?

The German beer purity law associated with beer sold at Oktoberfest is the Reinheitsgebot.

The Reinheitsgebot is commonly translated as the German Beer Purity Law. The best-known version dates to 1516, although Munich had an earlier local purity ordinance from 1487. In its traditional form, the rule restricted beer ingredients to water, barley and hops; yeast was understood later because its role in fermentation was not yet scientifically known.

Oktoberfest beer has an additional local requirement: the festival’s beer comes from approved Munich breweries. The six traditional suppliers are Augustiner, Hacker-Pschorr, Hofbräu, Löwenbräu, Paulaner and Spaten. Their Oktoberfest beer must comply with the relevant Munich and German purity standards.

A common misconception is that the Reinheitsgebot alone determines the beer’s flavour or style. It governs ingredients and brewing standards, while the characteristic modern Oktoberfest beer is generally a pale, strong lager often called Festbier. Radlers and non-beer drinks served at the festival are not themselves Oktoberfest beer.