Gaj [ɡai̯] is a settlement in the administrative district of Gmina Pelplin, within Tczew County, Pomeranian Voivodeship, in northern Poland. It lies approximately 3 kilometres (2 mi) south-east of Pelplin, 21 km (13 mi) south of Tczew, and 51 km (32 mi) south of the regional capital Gdańsk.

For details of the history of the region, see History of Pomerania.