Zásada (German: Sassadel) is a market town in Jablonec nad Nisou District in the Liberec Region of the Czech Republic.

Either the name was derived from the word zásada, which denoted a place where hunters lie in wait for game; or from the verb zasaditi se, which meant "to settle down"; or from the expression zasaditi hranice, i.e. "to mark boundaries".

[2] Zásada is located about 7 kilometres (4 mi) east of Jablonec nad Nisou and 15 km (9 mi) east of Liberec.

The highest point is on the slope of the Pustina mountain at 769 m (2,523 ft) above sea level.

The most important monument of Zásada is the Chapel of Saint Procopius.