Upatissa 優波底沙 (Pāli Upatissa; the Chinese gloss “Great Light” 大光 reflects an interpretation of the name as derived from a root meaning “light/brilliance”; CANWWW key AUT00304) was a Sinhalese Theravāda thera of uncertain dates, traditionally placed in the late first to early second century CE. He is known as the author of the Vimuttimagga (Path of Liberation 解脫道論; KR6o0052), a comprehensive meditation manual structured as an exposition of sīla, samādhi, and paññā. The Vimuttimagga survives complete only in the Liáng-period Chinese translation by 僧伽婆羅 (Saṃghabhara, completed c. 505–520); brief Tibetan fragments and Pāli citations preserve only small portions of the original. Modern scholars (notably P. V. Bapat and Peter Skilling) have argued that Upatissa was likely associated with the Abhayagiri-vihāra of Anurādhapura — the rival of the Mahāvihāra and ultimately suppressed by it — rather than with the Mahāvihāra itself, on the basis of doctrinal differences between the Vimuttimagga and Buddhaghosa’s later Visuddhimagga. He is not the same person as the Vinaya master Upatissa cited in the Cūḷa-vagga of the Dīpavaṃsa, nor the elder Upatissa who was the original name of Sāriputta. His Vimuttimagga is the only surviving complete witness to pre-Buddhaghosa Theravāda meditation theory, and is a foundational document for the modern reconstruction of Sri Lankan Buddhist intellectual history.