381 (CCCLXXXI) was a common year starting on Friday of the Julian calendar, the 381st year of the Common Era (CE) and Anno Domini (AD) designations, the 381st year of the 1st millennium, the 81st year of the 4th century, and the 2nd year of the 380s decade. As of the start of 381, the Gregorian calendar was 1 day ahead of the Julian calendar, which was the dominant calendar of the time.

• Roman Emperor Gratian moves the capital to Mediolanum (modern Milan).
• The Visigothic chieftain Athanaric becomes the first foreign king to visit the East Roman capital of Constantinople.
• Flavian succeeds Meletius as Patriarch of Antioch.
• Timothy succeeds Peter as Patriarch of Alexandria.

• Helian Bobo, emperor of the Chinese Xiongnu state Xia

• Athanaric, king of the Visigoths