DEMETRIUS III., called Eucerus, also Euergetes and Philometor, king of Syria, was the fourth son of Antiochus Grypus. By the assistance of Ptolemy Lathyrus he recovered part of his Syrian dominions from Antiochus Eusebes, and held his court at Damascus. He assisted the Jews against Alexander Jannaeus. In attempting to dethrone his brother Philip he was defeated by the Arabs and Parthians and taken prisoner. He was kept in confinement in Parthia by king Mithridates until his death.