Nāgārjuna (Lóngshù 龍樹, “Dragon-Tree”; alternate Chinese 龍勝, Lóngshèng, “Dragon-Victorious”) is the most consequential figure of the Mahāyāna Buddhist philosophical tradition. Conventionally dated to the second century CE (c. 150 – 250) — though more recent scholarship (Jan Yün-hua, Joseph Walser, Tom Tillemans) has suggested both earlier and later possibilities, with the secure historical anchor being the Mūlamadhyamakakārikā and a small core of associated texts — Nāgārjuna is credited as the founder of the Madhyamaka (Middle Way) school of Buddhist philosophy.
The Chinese tradition (per the Lóng-shù pútísà zhuàn 龍樹菩薩傳, T2047, an early-fifth-century Chinese hagiography by Kumārajīva or attributed to him) places Nāgārjuna in South India (Vidarbha or further south); a brāhmaṇa by birth, he was famously associated with the nāga palace from which (per the legend) he retrieved the [[KR6e0001|Avataṃsaka-sūtra]] (the legend reproduced by 吉藏 Jízàng in his [[KR6e0002|Huāyán yóu yì]]) and the Prajñāpāramitā literature.
His most consequential extant works are: the Mūlamadhyamaka-kārikā 中論 (T1564, in Kumārajīva’s translation by 鳩摩羅什 Kumārajīva); the Vigrahavyāvartanī (preserved only in Tibetan and Sanskrit, with no Chinese translation); the Yuktiṣaṣṭikā (T1575, in Tang translation); the Śūnyatāsaptati; the Dvādaśadvāra-śāstra 十二門論 (T1568, Kumārajīva); the Mahāprajñāpāramitā-śāstra / Dà zhì dù lùn 大智度論 (T1509, Kumārajīva, the great commentary on the Pañcaviṃśati-prajñāpāramitā); the [[KR6e0059|Daśabhūmika-vibhāṣā / Shí zhù pípóshā lùn 十住毘婆沙論]] (T1521, Kumārajīva, the great commentary on the Daśabhūmika-related material); and a very large corpus of less-well-attested or pseudepigraphic works.
Nāgārjuna’s doctrinal contribution — the doctrine of the two truths (conventional and ultimate), the doctrine of emptiness (śūnyatā) of all dharmas, and the rigorous application of dialectical reasoning to the metaphysical concepts of Indian Buddhist philosophy — is the foundation of all subsequent East Asian Mahāyāna scholasticism. In China his influence is direct (through Kumārajīva’s translations of his works, which provided the basis for the Sān-lùn 三論 / Three-Treatise school) and indirect (through the Mahāyāna doctrinal apparatus that he shaped). In the Huáyán tradition he is credited with retrieving the Avataṃsaka itself from the nāga palace; in Tantric Buddhism he is credited with founding several Tantric lineages. In Tibet he is the lineage-founder of the dBu ma (Madhyamaka) tradition.