The Lužnička (German: Lausur) is a stream in the Czech Republic and Germany, a right tributary of the Mandau River.

The Lužnička originates in the territory of Krásná Lípa in the Lusatian Mountains, at an elevation of 520 m (1,710 ft).

The longest tributaries of the Lužnička are:[4] Most of the river bed is significantly modified and bank stabilization is carried out.

The pond and its surroundings is protected as the Velký rybník Nature Reserve on an area of 103.7 ha (256 acres).

The area of wetlands, reedbeds, waterlogged meadows and wet forest is an important migration route for migratory birds.