Diodotus I Soter (c. 285 BCE – c. 239 BCE), Seleucid satrap of Bactria, rebels against Seleucid rule soon after the death of Antiochus II in c. 255 or 246 BCE, and wrests independence for his territory.

He dies in 239 BCE.

This event is recorded by Trogus, Prol.

41; Justin xli.

4, 5, where he is called Theodotus; Strabo xi.

515).

The name apparently is related to the title, Soter, that he uses for himself.

His power seems to have extended over the neighboring provinces.

Diodotus is a contemporary, a neighbor, and probably an ally of Andragoras, the satrap of Parthia, who at about the same time also proclaims independence from the Seleucid Empire.