The Zweihänder (German pronunciation: [t͡svaɪhɛndɐ] ⓘ, literally two-hander), also Doppelhänder (double-hander), Beidhänder (both-hander),[1] Bihänder, or Bidenhänder, is a large two-handed sword that was used primarily during the 16th century.

Zweihänder swords developed from the longswords of the Late Middle Ages and became the hallmark weapon of the German Landsknechte from the time of Maximilian I (d. 1519) and during the Italian Wars of 1494–1559. The Goliath Fechtbuch (1510) shows an intermediate form between longsword and Zweihänder.

This represented the final stage in the trend of making very large swords, which started in the 14th century, and ended in the 16th century. In its developed form, the Zweihänder acquired the handling characteristics of a polearm rather than a sword due to its increased size and weight, therefore adding to its striking power and longer reach. Consequently, it was not carried in a sheath, but across the shoulder like a pike or halberd.