|Centuries:||3rd century – 4th century – 5th century|
|Decades:||280s 290s 300s – 310s – 320s 330s 340s|
|Years:||312 313 314 – 315 – 316 317 318|
|315 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1068|
|Chinese calendar||甲戌年 (Wood Dog)
3011 or 2951
— to —
乙亥年 (Wood Pig)
3012 or 2952
|- Vikram Samvat||371–372|
|- Shaka Samvat||237–238|
|- Kali Yuga||3416–3417|
|Iranian calendar||307 BP – 306 BP|
|Islamic calendar||316 BH – 315 BH|
|Minguo calendar||1597 before ROC
|Seleucid era||626/627 AG|
|Thai solar calendar||857–858|
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.
- Constantine the Great and co-emperor Licinius battle the Sarmates, the Goths and the Carpians along the Danube. Constantine leads a punitive expedition into Dacia and reestablished the Roman fortifications of the frontier.
- July 25 – The Arch of Constantine is completed near the Colosseum at Rome to commemorate Constantine's victory over Maxentius at the Milvian Bridge. As part of the ceremony Constantine is expected to make a sacrifice to Rome's traditional gods, but he refuses to do so.
- Constantine I dedicated the Basilica of Maxentius and installs a large statue of himself inside it.
- Crucifixion is abolished as punishment in the Roman Empire.
- A program of assistance to the poor is established in the Roman Empire.
- Immense baths are constructed in Augusta Treverorum (modern Trier).
- Eusebius becomes bishop of Caesarea (approximate date).
- The lamb becomes the symbol of Jesus in Christian art.
- Cyril of Jerusalem, bishop and theologian (approximate date)
- Flavius Hannibalianus, king of Armenia and Pontus (d. 337)
- Himerius, Greek sophist and rhetorician (d. 386)
- Vettius Agorius Praetextatus, Roman politician (d. 384)