King of Magadha and father of Kāḷāsoka. He reigned for eighteen years (Mhv.iv.6; but see Dpv.v.98, where his reign is given as ten years, in the eighth year of which Dāsaka Thera died. Cf. Sp.i.33.).
According to the Mahāvaṃsa Ṭīkā (M.T.155 f), he was the son of a Licchavi rājā and a courtesan. When he was born he looked like a lump of flesh, and his mother gave orders that he should be put in a vessel and cast on the rubbish heap. The Nāga-king of the city kept guard over the vessel, but when the people crowded round him and said “Su-sū,” he left it and went away. In the crowd was a minister’s son, and, when the vessel was opened and the child was discovered, he decided to adopt him. In due course the child grew up, and when the infuriated populace deposed the parricide Nāgadāsaka, they placed Susunāga on the throne. He was called Susunāga because he was guarded by the Nāga who disappeared when the people said “Su-sū.”