Onuškis is a rural Town in Trakai District Municipality, in Vilnius County, Lithuania. Onuškis lies at 147 m above sea level. It has 421 inhabitants (2021). The nearest city is Alytus, 37 km to the west. Among the landmarks around are Trakai Island Castle (29 km), Basilica of the Visitation of the Blessed Virgin Mary (28 km) and Trakai Kenesa (29 km).