Nāgārjuna 龍樹 (c. 150 – c. 250 CE) - Indian Mahāyāna Buddhist thinker, scholar-saint and philosopher. He is widely considered as one of the most important Buddhist thinkers and teachers after the Buddha himself.
For a contemporary biography of Nāgārjuna, see the attached article entry from Brill’s Encyclopedia of Buddhism:
Nagarjuna_in_Brills_Encyclopedia_of_Bud (1).pdf381.7KB