Vācaka Umāsvāti, also spelled as Vācaka Umasvati and known as Vācaka Umāsvāmī, was an Indian scholar, possibly between the 2nd and 5th centuries CE, known for his foundational writings on Jainism. He authored the Jainatext Tattvartha Sutra (literally '"All That Is", also called Tattvarthadhigama Sutra). According to historian Moriz Winternitz, Umāsvāti may have been a Śvetāmbara ascetic as his views correspond more with the Śvetāmbara sect than with the Digambara sect, and that the latter is 'hardly entitled to claim him.' Umāsvāti's work was the first Sanskrit language text on Jaina philosophy, and is the earliest extant comprehensive Jaina philosophy text accepted as authoritative by all four Jaina traditions. His text has the same importance in Jainism as Vedanta Sutras and Yogasutras have in Hinduism.
Umāsvāti is claimed by both the Digambara and Śvētāmbara sects of Jainism as their own. However, several Jaina scholars consider him to be a Śvetāmbara ascetic. On the basis of his genealogy, he was also called Nagaravachka. Umāsvāti was influential not only in Jainism, but also other Indian traditions over the centuries. The 13th- to 14th-century Madhvacharya, founder of Dvaita Vedanta school of Hindu philosophy, for example referred to Umāsvāti in his works as Umasvati-Vācakācārya. Some in the Digambara Jaina tradition believe him to be the chief disciple of Acharya Kundakunda. However, this is disputed by several Indian as well as Western scholars. According to Ramesh Chandra Gupta, a Digambara scholar, Śvetāmbaras' version of Umāsvāti's biography is accepted over their Digambara counterparts.
