(Σέλενκος), king of SYRIA, was the eldest son of Demetrius II., and assumed the royal diadem immediately on learning the death of his father, B. C. 125; but his mother Cleopatra, who had herself put Demetrius to death, was indignant at hearing that her son had ventured to take such a step without her authority, and caused Seleucus also to be assassinated. His death appears to have followed almost immediately after that of his father, though some of the chronologers erroneously ascribe the duration of a year to his reign. (Appian, Syr. 68, 69 ; Justin, 39.1 ; Liv. Epit. lx.; Euseb. Arm. p. 168; Porphyr. ap. Euseb. l.c.)