(Ἀντίπατρος), second son of CASSANDER, king of Macedonia, by Thessalonica, sister of Alexander the Great. Soon after the death of Cassander (B. C. 296), his eldest son Philip also died of consumption (Paus. 9.7; Plut. Demetr. 905, f.), and great dissensions ensued between Antipater and his younger brother Alexander for the government. Antipater, believing that Alexander was favoured by his mother, put her to death. The younger brother upon this applied for aid at once to Pyrrhus of Epeirus and Demetrius Poliorcetes. Pyrrhus arrived first, and, exacting from Alexander a considerable portion of Macedonia as his reward, obliged Antipater to fly before him. According to Plutarch, Lysimachus, king of Thrace, Antipater's father-in-law, attempted to dissuade Pyrrhus from further hostilities by a forged letter purporting to come from Ptolemy Soter. The forgery was detected, but Pyrrhus seems notwithstanding to have withdrawn after settling matters between the brothers; soon after which Demetrius arrived. Justin, who says nothing of Pyrrhus, tells us, that Lysimachus, fearing the interference of Demetrius, advised a reconciliation between Antipater and Alexander. On the murder of Alexander by Demetrius, the latter appears, according to Plutarch, to have been made king of all Macedonia, to the exclusion at once of Antipater. According to Justin, Lysimachus conciliated Demetrius by putting him in possession of Antipater's portion of the kingdom, and murdered Antipater, who appears to have fled to him for refuge. The murder seems, from Diodorus, to have been owing to the instigation of Demetrius. (Plut. Pyrr. p. 386, Demetr. pp. 905, 906; Just. 16.1, 2; Diod. Sic. xxi. Exc. 7.)