Oktoberfest beer or Märzen is a traditional bottom fermented Austrian Lager based on the Schwechater Lagerbier developed in 1837 by Anton Dreher. The style was later popularized in Bavaria and in North American by German immigrants.

The German style is most often characterized by a medium to full body, a malty flavor balance, an amber range of color, and a clean dry finish, though wide variations are notable amongst German breweries marketing Märzen. Amongst these variations are colors ranging from pale to deep amber.

The North American style normally exhibits a stronger, though not aggressive, hop aroma and bitterness balance. The Austrian style closely resembles a Helles in color, body, and flavor balance, and is the most popular beer style in Austria.

Other common names for Märzen include:

• Maerzen
• Märzenbier
• Festbier
• Oktoberfestbier
• Wiener Märzen