1. A son of Pelops and Hippodameia, brother of Atreus and Thyestes, first married Pyrgo and afterwards Euaechme, and was the father of Echepolis, Callipolis, Iphinoë, Periboea, and Automedusa. (Paus. i. 42. § 1, 4, 43. § 4; Apollod. ii. 4. § 11, iii. 12. § 7.) Pausanias (i. 41. § 4) relates that, after Euippus, the son of king Megareus, was destroyed by the Cythaeronian lion, Megareus, whose elder son Timalcus had likewise fallen by the hands of Theseus, offered his daughter Euaechme and his kingdom to him who should slay that lion. Alcathous undertook the task, conquered the lion, and thus obtained Euaechme for his wife, and afterwards became the successor of Megareus. In gratitude for this success, he built at Megara a temple of Artemis Agrotera and Apollo Agraeus. He also restored the walls of Megara, which had been destroyed by the Cretans. (Paus. i. 41. § 5.) In this work he was said to have been assisted by Apollo, and the stone, upon which the god used to place his lyre while he was at work, was even in late times believed, when struck, to give forth a sound similar to that of a lyres.( i. 4. § 1 ; Ov. Met. viii. 15, &c.; Virg. Cir. 105; Theogn. 751.) Echepolis, one of the sons of Alcathous, was killed during the Calydonian hunt in Aetolia, and when his brother Callipolis hastened to carry the sad tidings to his father, he found him engaged in offering a sacrifice to Apollo, and thinking it unfit to offer sacrifices at such a moment, he snatched away the wood from the altar. Alcathous imagining this to be an act of sacrilegious wantonness, killed his son on the spot with a piece of wood. (Paus. i. 42. § 7.) The acropolis of Megara was called by a name derived for that of Alcathous. (i. 42. § 7.)
2. A son of Porthaon and Euryte, who was slain by Tydeus. (Apollod. i. 7. § 10, 8. § 5 ; Diod. iv. 65.)
3. A son of Aesyetes and husband of Hippodameia, the daughter of Anchises and sister of Aeneas, who was educated in his house. (Hom. Il. xiii. 466.) In the war of Troy he was one of the Trojan leaders, and was one of the handsomest and bravest among them. (Il. xii. 93, xiii. 427.) He was slain by Idomeneus with the assistance of Poseidon, who struck Alcathous with blindness and paralyzed his limbs so that he could not flee. (Il. xiii. 433, &c.)
4. Another personage of this name is mentioned by Virgil, Aen. x. 747.