Selargius, Ceràrgius or Ceràxius in Sardinian, is a comune (municipality) in the Province of Cagliari in the Italian region Sardinia, located about northeast of Cagliari. At 2011 national census it had 28,970 inhabitants.
The village exists since the Middle Ages as part of the Cagliari Campidanu Part of the Cagliari Judicatus. In 1928 it was merged by the Cagliari commune but gained again its autonomy in 1947, after a local referendum. Selargius is part of the Cagliari metropolitan area.
The municipality of Selargius contains some frazioni (subdivisions): Su Pezzu Mannu, Is Corrias and Su Planu.
Selargius borders the following municipalities: Cagliari, Monserrato, Quartu Sant'Elena, Quartucciu, Sestu, Settimo San Pietro.