The oldest and most important of the Commentaries on the Tipitaka, brought, according to tradition, to Ceylon by Mahinda, who translated it into Singhalese (Cv.xxxvii.228f). It thus came to be called the Sīhalatthakathā. Besides exegetical material on the Pāli Canon, it contained also historical materials on which were later based the Pāli Chronicles, the Mahāvamsa and the Dīpavamsa. For a description see Geiger's Dipavamsa and Mahavamsa, pp. 44, 63, etc.
The Mahā-atthakathā was the chief source from which Buddhaghosa drew his materials for his Commentaries and is often referred to in his works, particularly in the Samantapāsādikā. E.g., Sp.i.2; ii.494; 265; iii.537, 616, 617, 627, 701, 716, 718, 726; iv. 744, 776, 783, 817, 863, 914, 923; DhSA.157; DA.i.180, etc.
The Mahā-atthakathā was in charge of the monks of the Mahāvihāra at Anurādhapura. It was superseded by the Commentaries of Buddhaghosa, Dhammapāla and others, and is not now extant. It is often referred to merely as Atthakathā. E.g., VibhA.56, 155, 200, etc.