Eumenes II, fl. 2d cent. BC, son of Attalus I, king of Pergamum (197–159 BC). He managed to expand the wealth and prestige of his state by maintaining an allegiance with Rome for much of his reign. For his assistance in the Roman victory over Antiochus III of Syria, he received all of Antiochus's possessions as far as Taurus. He fell out of favor, however, during the Roman war with Macedonia, because he was suspected of plotting with the enemy. Only his death prevented a war between Pergamum and Rome. A vigorous ruler and an adept politician, Eumenes II helped make Pergamum an important cultural center, which included a library that was second only to that of Alexandria.