Gangesha Upadhyaya (Sanskrit: गंगेश उपाध्याय, Gaṅgeśa Upādhyāya) (late 12th century) was an Indianmathematician and philosopher from the kingdom of Mithila. He established the Navya-Nyāya ("New Logic") school. His Tattvacintāmaṇi (The Jewel of Thought on the Nature of Things) also known as Pramāṇacintāmaṇi (The Jewel of Thought on the Means of Valid Knowledge) is the basic text for all later developments. The logicians of this school were primarily interested in defining their terms and concepts related to non-binary logical categories.
Gengesha was born at Karion village on the banks of the river Kamala, 19 km south-east of Darbhanga in a Brahman family. According to tradition, he was illiterate in his early years but later he acquired the knowledge of logic as a boon from the goddess Kali. His son Vardhamana Upadhyaya was also a noted philosopher of the Nyaya school.
The text is divided into four khaṇḍas (books): Pratyakṣakhaṇḍa (book on perception), Anumānakhaṇḍa (book on inference), Upamānakhaṇḍa (book on comparison) and Śabdakhaṇḍa (book on verbal testimony). The first book opens with a salutation to Shiva.