Märzen is a German beer style from Bavaria that is closely connected with Oktoberfestbier and shares some similarities with Vienna lager. This style officially appeared in 1841 when it was brewed by Spaten brewery, but a similar style existed well before that.
Märzen is an amber-colored lager that has toasty malt aromas and flavors, dry finish, crisp hop bitterness, and a medium body. Original versions of these beers were somewhat darker, and as the name suggests—Märzen translates as March—they were brewed in March and then left to lager until early fall.
These versions were stronger and had more body than modern styles. Since it was available in autumn, it was first served during Oktoberfest. Although Märzen and Oktoberfestbier share many similarities, nowadays only six breweries in Germany—Augustiner, Hacker-Pschorr, Hofbräuhaus, Löwenbräu, Paulaner, and Spaten—are allowed to use the designation Oktoberfestbier and serve their brews at Oktoberfest.