Year 315 (CCCXV) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantinus and Licinianus (or, less frequently, year 1068 Ab urbe condita). The denomination 315 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

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• Flavius Hannibalianus, ruler of Armenia and Pontus (d. 337)
• Hilary of Poitiers, Christian bishop and Doctor of the Church^[1]
• Himerius, Greek sophist and rhetorician (approximate date)
• Vettius Agorius Praetextatus, Roman politician (d. 384)

• September 14 – Maternus of Cologne, bishop of Trier
• Du Tao (or Jingwen), Chinese general and rebel leader
• Galeria Valeria, Roman empress and wife of Galerius
• Prisca, Roman empress and wife of Diocletian (b. 247)
• Valerius of Saragossa, Christian bishop and martyr