With the traditional cry of "O'zapft is" ("The keg is tapped") at midday, Mayor Christian Ude cracked open the first barrel and handed a foamy litre-sized "Mass" glass to Bavaria's state premier, Horst Seehofer.
Long queues had formed around 8 am outside the bigger beer tents, two hours before the massive halls were to open and well before the suds began to flow.
Bavarian pilot Andreas Maffey, 33, said he was proud to be a part of the festival. "We have the privilege and the luck to have the world's biggest festival on our doorstep," he said.
"I reserve a table every day during the Oktoberfest but I can't come every day - my liver wouldn't take it," he joked, adding he expected nonetheless to consume "around eight" litre-sized glasses.
American student Olivia Dassler had come all the way from her university in Italy for the experience. Wearing a pink "dirndl" - a long-pleated smock worn with low-cut blouse - she said the traditional dress was a must. "I've never been to Germany before, so when I think of Munich that's what I think of, the outfits. I know it's kind of stereotypical but they're so cool," she said.
More than six million people from around the world were expected to attend this year's festival and slurp between them around seven million litres of beer in one of the 35 giant beer tents stretching over 26 hectares.
They will also gobble literally tens of thousands of giant soft pretzels, pork dumplings and other traditional Bavarian delicacies.
Although the Oktoberfest started off 202 years ago, this year's event is only the 179th time it has been celebrated. The party was cancelled during two world wars, two cholera outbreaks, Napoleon's invasion of Bavaria and the hyperinflation of the 1920s.
The festival was originally held in October as the name suggests - to celebrate a royal wedding - but was brought forward by amonth to take advantage of better weather.