king of Sparta, 20th of the Eurypontids, was son of Agesilaus II. We first hear of him as interceding with his father in behalf of Sphodrias, to whose son Cleonymus he was attached, and who was thus saved, through the weak affection of Agesilaus, from the punishment which his unwarrantable invasion of Attica had deserved, B. C. 378. (Xen. Hell. 5.4. §§ 25_33 ; Diod. 15.29; Plut. Ages. 100.25; comp. Plut. Pel. 100.14.) In B. C. 371, he was sent, in consequence of the illness of Agesilaus (Xen. Hell. 5.4.58; Plut. Ages. 100.27), to succour the defeated Spartans at Leuctra; but Jason of Pherae had already mediated between them and the Thebans, and Archidanmus, meeting his countrymen on their return at Aegosthena in Megara, dismissed the allies, and led the Spartans home. (Xen. Hell. 6.4. §§ 17-26; comp. Diod. 15.54, 55; Wess. ad loc.; Thirlwall's Greece, vol. v. p. 78, note.) In 367, with the aid of the auxiliaries furnished by Dionysius I. of Syracuse, he defeated the Arcadians and Argives in what has been called the "Tearless Battle," from the statement in his despatches, that he had won it without losing a man (Xen. Hell. 7.1.28; Plut. Ages. 100.33; Polyaen. 1.45 ; Diod. 15.72); and to the next year, 366, must be taken assigned the "Archidamus" of Isocrates, written perhaps to be delivered by the prince in the Spartion senate, to encourage his country in her resolution of maintaining her claim to Messenia, when Corinth had made, with Sparta's consent, a separate peace with Thebes. (Xen. Hell. 7.4.9.) In 364, he was again sent against Arcadia, then at war with Elis (Xen. Hell. 7.4.20, &c.; Just. 6.5); and in 362, having been left at home to protect Sparta while Agesilaus went to join the allies at Mantineia, he baffled the attempt of Epaminondas on the city. (Xen. Hell. 7.5.9, &c.; Diod. 15.82, 83; Plut. Ages.100.34; Isocr.Ep.ad Arch. § 5.) He succeeded his father on the throne in 361. In 356, we find him privately furnishing Philomelus, the Phocian, with fifteen talents, to aid him in his resistance to the Amphictyonic decree and his seizure of Delphi, whence arose the sacred war. (Diod. 16.24; Just. 8.1; comp. Paus. 4.4 ; Theopomp. apud Paus. 3.10.) In 352, occurred the war of Sparta against Megalopolis with a view to the dissolution (διοικισμός) of that community ; and Archidamus was appointed to the command, and gained some successes, though the enterprise did not ultimately succeed. (Diod. 16.39; Paus. 8.27; Demosth. pro Megal. ; comp. Aristot. Pol. 5.10, ed. Bekk.) In the last year of the sacred war, 346, we find Archidamus marching into Phocis at the head of 1000 men. According to Diodorus (16.59), the Phocians had applied for aid to Sparta, but this seems questionable from what Aeschines (de Fals. Leg. p. 45) reports as the ad vice of the Phocian leaders to Archidamus, "to alarm himself about the dangers of Sparta rather than of Phocis." Demosthenes (de Fals. Leg. p.365) hints at a private understanding between Philip and the Spartans, and at some treachery of his towards them. Whether however on this account, or as being distrusted by Phalaecus (Aesch. de Fals. Leg. p. 46), or as finding it impossible to effect anything on behalf of the Phocians, Archidamus, on the arrival of Philip, withdrew his forces and returned home. In 338, he went to Italy to aid the Tarentines against the Lucanians, and there he fell in battle on the very day, according to Diodorus, of Philip's victory at Chacroneia. (Diod. 16.63, 88; Paus. 3.10; Strab. vi. p.280; Theopomp. apud Athen. xii. p. 536c. d.; Plut. Agis 100.3.) The Spartans erected a statue of him at Olympia, which is mentioned by Pansanias. (vi. ch. 4, 15.)