(Θεόπομπος), king of Sparta, and 9th of the Eurypontids. His name is connected with two important but obscure events in Spartan history, viz. the establishment of the power of the ephors, and the first Messenian war. With respect to the former, it was about 130 years, according to Plutarch, after the legislation of Lycurgus, that the popular party obtained the ephoralty from Theopompus, as a check on the oligarchy; on which occasion he was reproached by his wife for his tameness in surrendering so large a portion of the royal prerogative, and defended himself by alleging that its limitation would ensure its continuance. (Plut. Lyc. 7 ; Aristot. Pol. 5.11, ed. Bekk.) From Plutarch, however, we also learn that Theopompus and his colleague Polydorus gave additional stringency to the Rhetra, which enjoined that the popular assembly should simply accept or reject the measures proposed by the senate and the kings, without introducing any amendment or modification of them; and from the oligarchical character of this act of Theopompus, Müller argues that the extended political power of the ephors could not have originated in his time. More satisfactory, however, is the explanation of Platner and Arnold, that the people obtained the institution of ephors by way of compensation for the Rhetra in question, and that " the king was obliged to confirm those liberties, which he had vainly endeavoured to overthrow." (Plut. Lyc. 6, comp. Cleom. 10 ; Müller, Dor. 3.5.8, 7.2; C. F. Hermann, Pol. Ant. ch. 2.43 ; Arnold, Thuc. vol. i. App. 2; G. C. Lewis, in the Philol. Museum, vol. ii. pp. 51, 52.) As to the first Messenian war, thus much appears from Tyrtaeus, that Theopompus was mainly instrumental in bringing it to a successful issue, though the inference of Pausanias, that he lived to complete the actual subjugation of Messenia, is more than the words of the poet warrant. They are, however, inconsistent with the date which Eusebius assigns to the death of Theopompus, viz. B. C. 740. Clinton gives, for the duration of his reign, about B. C. 770-720. But we can arrive at no certainty in the chronology of this period. According to the Messenian account, Theopompus was slain, not long before the end of the war, by Aristomenes, while the Spartan tradition was, that he was only wounded by him. We are accustomed, indeed, to regard Aristomenes as the hero of the second war; but this, after all, is a doubtful point. (Paus. 4, 6, &c.; Plut. Agis. 21 ; Müller, Dor. App. ix.; Clint. F. H. vol. ii. App. ch. 3; Grote's Greece vol. ii. pp. 558, 559.)