Son of Muṭasīva and viceroy of Devānampiyatissa. His wife was Anulā, for whose ordination Saṅghamittā came over from Jambudīpa (Mhv.xiv.56; Dpv.xi.6; xvii.75). His second wife was a foolish woman who tried to poison him in order to get the throne for her son. While he was building the Taraccha reservoir, she sent him some mangoes, the top one of which, intended for him, was poisoned. However, it was her son who ate the mango and died. Mahānāga thereupon went to Rohaṇa, where he founded the dynasty of that name at Mahāgāma. His son was Yatthālayaka Tissa. Mahānāga built the Nāgamahāvihāra and the Uddhakandara-vihāra. Mhv.xxii.2 ff.