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.

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• Murong Hui, Chinese general and prince of the Later Yan Dynasty (d. 397)
• Murong Sheng (or Daoyun), Chinese emperor of the Later Yan Dynasty (d. 401)
• Synesius of Cyrene, Christian bishop (approximate date)

• May 2 – Athanasius of Alexandria, Egyptian Coptic Orthodox bishop (b. 296)
• June 9 – Ephrem the Syrian, Syrian Orthodox priest and saint (b. 306)
• Huan Wen (or Yuanzi), Chinese general and regent (b. 312)
• Nerses I (the Great), Armenian catholicos (or patriarch)
• Sun Sheng, Chinese historian and politician (b. 302)