Decia may refer to :
- the Roman gens (Patrician clan) Decia, using the name Decius
- the Ancient city and bishopric Mopsuestia
- in Latin, feminine form of decius (the) 'tenth'
The gens Decia was a plebeian family of high antiquity, which became illustrious in Roman history by two of its members sacrificing themselves for the preservation of their country. The first of the family known to history was Marcus Decius, chosen as a representative of the plebeians during the secession of 495 BC.