Lomnice nad Popelkou (German: Lomnitz an der Popelka) is a town in Semily District in the Liberec Region of the Czech Republic. It has about 5,600 inhabitants. The town is located on the Popelka Stream, on the border between the Giant Mountains Foothills and Ještěd–Kozákov Ridge. The historic town centre is well preserved and is protected as an urban monument zone. The locality of Karlov is protected as a village monument reservation.