Vialonga is a town and freguesia (civil parish) in the municipality of Vila Franca de Xira, Portugal.

[1] The land where present-day Vialonga stands was occupied by humans in prehistoric ages, as evidenced by the dolmen cemeteries in Monte Serves and Casal do Penedo in the Vialonga parish.

Other prehistoric religious objects, ornaments, metallic weapons and ceramics have been found in the area.

[2] It is believed that the settlement in this area comes from the times of Moorish rule in the Iberian Peninsula.

[2] In November 2014, Vialonga was one of the locations most affected by a Legionella outbreak in the Vila Franca de Xira municipality.