Gmina Radzymin is an urban-rural gmina (administrative district) in Wołomin County, Masovian Voivodeship, in east-central Poland. Its seat is the town of Radzymin, which lies approximately 9 kilometres (6 mi) north-west of Wołomin and 26 km (16 mi) north-east of Warsaw.
The gmina covers an area of 130.93 square kilometres (50.6 sq mi), and as of 2006 its total population is 19,129 (out of which the population of Radzymin amounts to 7,864, and the population of the rural part of the gmina is 11,265).