Zwieback (German: [ˈt͡sviːbak] ⓘ) is a form of rusk eaten in Austria, Belgium, Bosnia-Herzegovina, Bulgaria, Croatia, France, Germany, Greece, Italy, Luxembourg, The Netherlands, North Macedonia, Poland, Scandinavia, Serbia, Slovenia, Switzerland and Turkey.

According to Fabian Scheidler, Albrecht von Wallenstein invented zwieback to feed his mercenary army during the Thirty Years' War.

[2] Zwieback is commonly used to feed teething babies [2] and as the first solid food for patients with an upset stomach.

Russian Mennonite zwieback, called Tweebak in Plautdietsch, is a yeast bread roll formed from two pieces of dough that are pulled apart when eaten.

Traditionally, this type of zwieback is baked Saturday and eaten Sunday morning and for afternoon Faspa (Standard German: "Vesper"),[4] a light meal.