The Sthavira nikāya was one of the early Buddhist schools. The Sthavira nikāya split away from the majority Mahāsāṃghikas during the Second Buddhist council resulting in the first schism in the Sangha. The MahāsāṃghikaŚāriputraparipṛcchā, a text written to justify this school's departure from the disciplinary code of the elder monks, asserts that the council was convened at Pāṭaliputra over matters of vinaya, and it is explained that the schism resulted from the majority refusing to accept the addition of rules to the Vinaya by the minority. The Mahāsāṃghikas therefore saw the Sthaviras as being a breakaway group which was attempting to modify the original Vinaya. Scholars have generally agreed that the matter of dispute was indeed a matter of vinaya, and have noted that the account of the Mahāsāṃghikas is bolstered by the vinaya texts themselves, as vinayas associated with the Sthaviras do contain more rules than those of the Mahāsāṃghika Vinaya. Modern scholarship therefore generally agrees that the Mahāsāṃghika Vinaya is the oldest. According to Skilton, future scholars may determine that a study of the Mahāsāṃghika school will contribute to a better understanding of the early Dhamma-Vinaya than the Theravada school.
The Theravāda school of Sri Lanka and Southeast Asia has identified itself exclusively with the Sthaviras, as the Pali word thera is equivalent to the Sanskrit sthavira. This has led early Western historians to assume that the two parties are identical. However, this is not the case, and by the time of Ashoka, the Sthavira sect had split into the Sammitīya Pudgalavada, Sarvāstivāda, and the Vibhajyavāda schools. The Vibhajyavāda school is believed to have split into other schools as well, such as the Mahīśāsaka school and the ancestor of the Theravada school. According to Damien Keown, there is no historical evidence that the Theravada school arose until around two centuries after the Great Schism which occurred at the Third Council.
Theravādin accounts
Starting with the Dīpavaṃsachronicle in the 4th century, the Theravādins of the Mahāvihāra in Sri Lanka attempted to identify themselves with the original Sthavira sect. The Theravādin Dīpavaṃsa clarifies that the name Theravāda refers to the "old" teachings, making no indication that it refers to the Second Council. Similarly, the name Mahāsāṃghika is in reference to those who follow the original Vinaya of the undivided Saṃgha. The Dīpavaṃsa chronicle lauds the Theravāda as a "great banyan" and dismissively portrays the other early Buddhist schools as thorns. Dīpavaṃsa, 4.90–91 says: According to the Mahāvaṃsa, a Theravādin source, after the Second Council was closed those taking the side of junior monks did not accept the verdict but held an assembly of their own attended by ten thousand calling it a Mahasangiti from which the school derived its name Mahāsāṃghika. However, such popular explanations of Sthavira and Mahāsāṃghika are generally considered folk etymologies. Bhante Sujato explains the relationship between the Sthavira sect and the Theravāda:
