Joniškis District Municipality is a territorial unit of Lithuania with a population of about 30,000. The administrative center of the municipality is the city of Joniškis.

Joniškis is a city in northern Lithuania with a population of about 9,900. It is located 39 kilometers north of Šiauliai and 14 kilometers south of the Lithuania–Latvia border. Joniškis is the municipal and administrative centre of Joniškis district municipality.