Gmina Nidzica is an urban-rural gmina (administrative district) in Nidzica County, Warmian-Masurian Voivodeship, in northern Poland. Its seat is the town of Nidzica, which lies approximately 48 kilometres (30 mi) south of the regional capital Olsztyn. The gmina covers an area of 378.88 square kilometres (146.3 sq mi), and as of 2006 its total population is 21,485 (out of which the population of Nidzica amounts to 14,761, and the population of the rural part of the gmina is 6,724).