Rokytnice nad Jizerou (German: Rochlitz an der Iser) is a mountain resort in the west part of the Giant Mountains in the Czech Republic. The town is located in the Liberec Region, in the Semily District, in elongated valleys of Huťský stream between mountains massifs Stráž (782 m), Čertova hora (1022 m) and Lysá hora (1344 m) and along the left (east) bank of the river Jizera.
In winter Rokytnice is also one of the most famous ski resorts in the Czech Republic, with many ski schools and 28 lifts. The dominant Lysá Hora has 8 lifts and 17 ski runs. The official ski runs in Rokytnice are the longest in the Czech Republic.