The Lusatian Neisse (German: Lausitzer Neiße; Polish: Nysa Łużycka; Czech: Lužická Nisa; Upper Sorbian: Łužiska Nysa; Lower Sorbian: Łužyska Nysa), or Western Neisse, is a 252-kilometre (157 mi) river in northern Central Europe. It rises in the Jizera Mountains, near Nová Ves nad Nisou, at the Czech border becoming the Polish–German border for its remaining 197 kilometres (122 mi), to flow into the similarly northward-flowing Oder from the left.
Its drainage basin covers 4,403 km (1,700 sq mi), of which 2,201 km (850 sq mi) is in Poland, the rest is mainly in Germany. The river reaches the tripoint of the three nations by Zittau, a German town/city, after 54 kilometres (34 mi), leaving the Czech Republic. It is a left-bank tributary of the Oder, into which it flows between Neißemünde-Ratzdorf and Kosarzyn – north of the towns of Guben and Gubin. The river was a motivations to found Gubin as a craftmanship and trading port in the 13th Century.