Catius (fl. 50s–40s BC?) was an Epicurean philosopher, identified ethnically as an Insubrian Celt from Gallia Transpadana. Epicurean works by Amafinius, Rabirius, and Catius were the earliest philosophical treatises written in Latin. Catius composed a treatise in four books on the physical world and on the highest good (De rerum natura et de summo bono).