One of the books, generally the fifth, of the Khuddaka Nikāya.
It consists of five Vaggas - Uraga, Cūla, Mahā, Atthaka and Pārāyana - the first four consisting of fifty four short lyrics, while the fifth contains sixteen suttas. Of the thirty eight poems in the first three cantos, six are found in other books of the canon, showing that they had probably existed separately, as popular poems, before being incorporated in the Sutta Nipāta. The fourth canto is referred to in the Samyutta Nikaya, the Vinaya Pitaka and the Udāna, as a separate work, and this canto was probably very closely associated with the last, because the Niddesa is obviously an old Commentary on them and takes no notice of the remaining cantos. (For a detailed account see Law, Pāli Literature i.232f.)
The Dīghabhānakas included the Sutta Nipāta in the Abhidhamma Pitaka (DA.i.15).
A Commentary exists on the Sutta Nipāta, written by Buddhaghosa, and called the Paramatthajotikā (q.v.).