|Centuries:||3rd century – 4th century – 5th century|
|Decades:||340s 350s 360s – 370s – 380s 390s 400s|
|Years:||370 371 372 – 373 – 374 375 376|
|373 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1126|
|Chinese calendar||壬申年 (Water Monkey)
3069 or 3009
— to —
癸酉年 (Water Rooster)
3070 or 3010
|- Vikram Samvat||429–430|
|- Shaka Samvat||294–295|
|- Kali Yuga||3473–3474|
|Iranian calendar||249 BP – 248 BP|
|Islamic calendar||257 BH – 256 BH|
|Minguo calendar||1539 before ROC
|Seleucid era||684/685 AG|
|Thai solar calendar||915–916|
Year 373 (CCCLXXIII) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Augustus and Valens (or, less frequently, year 1126 Ab urbe condita). The denomination 373 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.
- Emperor Valens is converted to Arianism and orders the persecution of orthodox Christians in the Roman East.
- Quintus Aurelius Symmachus becomes proconsul of Africa, and is made a member of the pontifical college.
- Count Theodosius is appointed commander of an expedition to suppress the rebellion of Firmus in Mauretania.
- Valens Aqueduct is inaugurated near Constantinople (modern Istanbul); the aqueduct has a length of 971 meters.
- Battle of the Tanais River: The Huns defeat the Alans near the Don, sending the remnants fleeing westward.
- King Shapur II declares war as a result of Valens' support of Armenia. Emperor Valens makes Antioch his military base for the campaign against Persia.
- Murong Hui, imperial prince of the Xianbei state Later Yan (d. 397)
- Murong Sheng, emperor of the Xianbei state Later Yan (d. 401)
- Synesius, bishop of Ptolemais (approximate date)
- Nicklas Kirkevall, Lord of Auwrarw
- May 2 – Athanasius of Alexandria, bishop and opponent of Arianism
- June 9 – Ephrem the Syrian, Christian saint and hymn writer
- Huan Wen, general of the Jin Dynasty (b. 312)