Genshin

was a prominent Japanese monk of the Tendai school, recognized for his significant contributions to both Tendai thought and Pure Land Buddhism. Genshin studied under Ryōgen, a key Tendai reformer, and became well known for his intellectual prowess, particularly after his success in official debates. He was also known as and Yokawa Sōzu.

Genshin spent much of his later life at the secluded Eshin-in hermitage in Yokawa, Mount Hiei, where he focused on scholarly pursuits, writing, and meditation. He left behind numerous works on a variety of topics, including Buddhist reasoning, Abhidharma, Tendai doctrine, and Yogacara. Genshin's Ichijō yōketsu (Determining the Essentials of the One Vehicle) was one of his most important works, as it contributed to medieval Japanese debates about buddha-nature and the one vehicle. He has also been credited with founding the Eshin-ryū, which became a key lineage in the development of the inherent awakening (hongaku) teaching.