|Millennium:||1st millennium BC|
|Centuries:||5th century BC – 4th century BC – 3rd century BC|
|Decades:||420s BC 410s BC 400s BC – 390s BC – 380s BC 370s BC 360s BC|
|Years:||393 BC 392 BC 391 BC – 390 BC – 389 BC 388 BC 387 BC|
390 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Ambustus, Longus, Ambustus, Fidenas, Ambustus and Cornelius (or, less frequently, year 364 Ab urbe condita). The denomination 390 BC 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.