(Διόδοτος), King of Bactria, and founder of the Bactrian monarchy, which continued to subsist under a Greek dynasty for above one hundred and fifty years. This prince as well as his successor is called by Justin, Theodotus, but the form Diodotus, which occurs in Strabo (xi. p.515) seems to have been that used by Trogus Pompeius (Prol. Trogi Pompeii, lib. xli.), is confirmed by the evidence of an unique gold coin now in the museum at Paris. (See Wilson, Ariana, p. 219.)

Both the period and circumstances of the establishment of his power in Bactria are very uncertain. It seems clear, however, that he was at first satrap or governor of that province, under the Syrian monarchy, and that he took advantage of his sovereign's being engaged in wars in distant parts of his dominions to declare himself independent The remote and secluded position of his territories, and the revolt of the Parthians under Arsaces, almost immediately afterwards, appear to have prevented any attempt on the part of the Syrian monarch to reduce him again to subjection. At a later period, when Seleucus Callinicus undertook his expedition against Parthia, he appears to have entered into alliance with Diodotus, and may perhaps have confirmed him in the possession of his sovereignty, to secure his co-operation against Tiridates. Diodotus, however, died apparently just about this time. (Just. 41.4; Strab. xi. p.515; compare Wilson's Ariana, pp. 215-219; Droysen's Hellenismus, ii. pp. 325, 412, 760; Raoul Rochette Journ. des Sauans, Oct. 1835.)

With regard to the date of the revolt of Diodotus, it appears from Strabo and Justin to have preceded that of Arsaces in Parthia, and may therefore be referred with much probability to the latter part of the reign of Antiochus II. in Syria. B. C. 261-246. [See ARSACES, p. 354a.] The date usually received is 256 B. C., but any such precise determination rests only on mere conjecture.

Concerning the Bactrian kings in general see Bayer, Historia Regni Graecorum Bactriani, 4to. Petrop. 1738; Lassen, Zur Geschichte der Griechischen und Indo-Skytischen Könige in Baktrien, 8vo. Bonn, 1838; Wilson's Ariana Antiqua, 4to. Lond. 1841.