Hrádek nad Nisou (Czech pronunciation: [ˈɦraːdɛk ˈnad ɲɪsou]; German: Grottau, Polish: Gródek nad Nysą) is a town in Liberec District in the Liberec Region of the Czech Republic.

The historic town centre is well preserved and is protected by law as an urban monument zone.

Hrádek nad Nisou consists of nine municipal parts (in brackets population according to the 2021 census):[2] The oldest forms of the name are Grad, Grat (in modern Czech hrad; meaning 'castle').

[3] Hrádek nad Nisou is located about 17 kilometres (11 mi) northwest of Liberec.

The municipal territory lies mostly in the Zittau Basin, but on the south it also extends to the Lusatian Mountains and Ještěd–Kozákov Ridge.

[5] Hrádek nad Nisou lies on the railway line heading from Liberec to Zittau and continuing to Varnsdorf or Dresden.

Hrádek nad Nisou has a well preserved town centre with many historic houses.