The Vajjika (Pāli: Vajjika) or Vrijika (IAST: Vṛjika) League, Confederacy, or Sangha, also called simply Vajji (Pāli: Vajji) or Vriji (IAST: Vṛji), was an ancient Indo-Aryan league which existed during the later Iron Age period in the north-eastern Indian subcontinent.

[2] According to Chinese pilgrim Xuanzang, the name Saṃvajji, meaning "united Vajjis," was given by the peoples of northern South Asia to the Vajjika League.

[2][5] The once popular view among scholars that the Vajjika League was constituted of eight clans was based on a misreading of the 5th century CE Buddhist commentator Buddhaghosa's mention that the legal tribunals of Vesālī included the aṭṭhakulika (अट्ठकुलिक), which was interpreted as meaning "eight tribes."

[8] The area of the Vajjika League was bounded to the north, east, south, and west, respectively, by the Himālaya mountains, and the Mahānanda, Gaṅgā, and Sadānirā rivers.

[6] Shortly before or during the lifetime of the Buddha, around the 7th or 6th century BCE, the Mahā-Videha kingdom was invaded by the Licchavikas, an Indo-Aryan tribe who temporarily occupied the Vaideha capital of Mithilā, from where they could best administer the territory of Videha.

The Licchavikas and the Mallakas were considered to be the republican states of Kāsī-Kosala by Jain sources, and both Mallaka republics joined the Licchavi-led Vajjika League to deal with danger they might have faced in common during periods of instability, and within which they held friendly relations with the Licchavikas, the Vaidehas, and the Nāyikas who were the other members of this league, although occasional quarrels did break out between these republics.

There were nevertheless occasional tensions between Licchavi and Magadha, such as the competition at the Mallaka capital of Kusinārā over acquiring the relics of the Buddha after his death.

After the failure of this rebellion, Vehalla sought refuge at his grandfather's place in the Licchavika and Vajjika capital of Vesālī, following which Ajātasattu repeatedly attempted to negotiate with the Licchavikas-Vajjikas.

Ajātasattu's hostility towards the Vajjika League was also the result of the differing forms of political organisation between Magadha and the Vajjika League, with the former being monarchical and the latter being republican, not unlike the opposition of the ancient Greek kingdom of Sparta to the democratic form of government in Athens, and the hostilities between the ancient Macedonian king Philip II to the Athenian and Theban republics.

The military forces of the Vajjika League were initially too strong for Ajātasattu to be successful against them, and it required him having recourse to diplomacy and intrigues over the span of a decade to finally defeat the Vajjika League by 468 BCE and annex its territories, including Licchavi, Videha, and Nāya to the kingdom of Magadha, while the Mallakas also became part of Ajātasattu's Māgadhī empire but were allowed a limited degree of autonomy in terms of their internal administration, and stopped existing as a republican tribe when the Maurya dynasty ruled Magadha or shortly after.