Zielonka [ʑɛˈlɔnka] is a town in Wołomin County, Masovian Voivodeship, Poland, with 17,398 inhabitants (2013). It is located about 13 km (8 mi) to the north-east of the centre of Warsaw.
Zielonka borders Warsaw and several other towns of the Warsaw metropolitan area: Ząbki and Marki in the west, Kobyłka in the north, and Sulejówek in the south. It was granted town rights in 1960.
Wołomin County (Polish: powiat wołomiński) is a territorial and administrative division in Masovian Voivodeship, east-central Poland. It came into being on January 1, 1999, as a result of the Polish local government reforms passed in 1998. The administrative seat of the county and also its largest town is Wołomin, which lies 22 kilometres (14 mi) north-east of Warsaw. The county contains six other towns: Ząbki, 11 km (7 mi) south-west of Wołomin, Marki, 10 km (6 mi) west of Wołomin, Kobyłka, 3 km (2 mi) south-west of Wołomin, Zielonka, 8 km (5 mi) south-west of Wołomin, Radzymin, 9 km (6 mi) north-west of Wołomin, and Tłuszcz, 18 km (11 mi) north-east of Wołomin.
The county covers an area of 955.37 square kilometres (368.9 sq mi). As of 2019 its total population is 247,288, out of which the population of Wołomin is 37,082, that of Ząbki is 37,219, that of Marki is 34,679, that of Kobyłka is 24,096, that of Zielonka is 17,588, that of Radzymin is 13,005, that of Tłuszcz is 8,156, and the rural population is 75,463.