|Millennium:||1st millennium BC|
|138 BC by topic|
|Wikimedia Commons has media related to 138 BC.|
Year 138 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Serapio and Callaicus (or, less frequently, year 616 Ab urbe condita). The denomination 138 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.
- Zhang Qian begins his explorations in central Asia for Chinese emperor Han Wu Di.
- The first Chinese diplomatic mission to the Ferghana valley, led by Chang Chien, is sent.
- Han Dynasty China intervenes in a war between the Minyue and Eastern Ou during its expansion southward.
- Valencia in Spain is founded as a Roman colony
Arts and sciences
- Hymn to Apollo is written and inscribed on stone in Delphi; it is the earliest surviving notated music, in a substantial and legible fragment, in the western world.
- Diodotus Tryphon (suicide)
- Mithridates I, King of Parthia (b. c. 195 BC)
- Attalus II Philadelphus, King of Pergamon (b. 220 BC)