King of Bactria, was the son of the GraecoBactrian king Euthydemus, for whom he negotiated a peace with Antiochus the Great in 206 (Polyb. xi. 34). Soon afterwards he crossed the Hindu Kush and began the invasion of India (Strabo xi. 516); he conquered the Punjab and the valley of the Indus down to the sea and to Gujerat. The town Sangala, a town of the Kathaeans in the Punjab (Arrian v. 22, 2 ff.), he named after his father Euthydemia (Ptol. vii. I, 46). That his power extended into Arachosia (Afghanistan) is proved by the name of a town Demetrias near Kandahar (Isidor. Charac. 19, cf. Strabo xi. 516). On his coins he wears an elephant's skin with trunk and teeth on his head; on bronze coins, which have also an Indian legend in Kharoshti letters (see BACTRIA), he calls himself the unvanquished king (BautXEws avudyroV Amunrpiov). One of his coins has already the square form used in India instead of the circular. Eventually he was defeated by the usurper Eucratides, who meanwhile had risen to great power in Bactria. About his death we know nothing; his young son Euthydemus II. (known only from coins) can have ruled only a short time. (ED. M.)