Diodotus I Soter was the first Hellenistic king of Bactria. Diodotus was initially satrap of Bactria, but became independent of the Seleucid empire around 255 BC, establishing the Greco-Bactrian Kingdom. In about 250 BC, Diodotus repelled a Parthian invasion of Bactria by Arsaces. He minted an extensive coinage and administered a powerful and prosperous new kingdom. He died around 235 BC and was succeeded by his son Diodotus II.