Janówek Pierwszy [jaˈnuvɛk ˈpjɛrfʂɨ] is a village in the administrative district of Gmina Wieliszew, within Legionowo County, Masovian Voivodeship, in east-central Poland. It lies approximately 13 kilometres (8 mi) west of Wieliszew, 10 km (6 mi) north-west of Legionowo, and 29 km (18 mi) north-west of Warsaw.

In 2005 the village had a population of 520.