Mūša (Latvian: Mūsa) is a river in Northern Lithuania and Southern Latvia (Zemgale region), having its confluence with river Nemunėlis (Latvian: Mēmele), in Latvia, near city Bauska. Mūša is a tributary of the river Lielupė. Mūša is 164 kilometres (146 km in Lithuania, 18 km in Latvia) long.