Tendai is a major school of Japanese Mahāyāna Buddhism, established in the early centuries of Japanese Buddhist history by the monk Saichō and grounded in the Chinese Tiantai tradition associated with Zhiyi. Its institutional and spiritual center developed on Mount Hiei near Kyoto, from which it exerted a formative influence on Japanese religious life. At the heart of its doctrinal vision stands the Lotus Sūtra, regarded as the supreme expression of the Buddha’s teaching and the key to understanding that all beings possess Buddha-nature and can attain enlightenment. This conviction that every being can realize Buddhahood in the midst of ordinary existence shapes both its philosophy and its practice.

Doctrinally, Tendai is renowned for its synthetic and inclusive approach. Drawing from Tiantai thought, it emphasizes the principle of “three thousand realms in a single moment of mind” (ichinen sanzen), a way of expressing the profound interconnectedness and interpenetration of all phenomena and the ever-present possibility of awakening. This framework is sometimes described as a “perfect teaching,” one that seeks to transcend narrow sectarian boundaries and to harmonize different paths without denying their distinctiveness. The Middle Way, avoiding extremes and affirming the non-duality of ultimate reality and the everyday world, provides the philosophical backbone for this synthesis.

In terms of practice, Tendai integrates a wide range of methods into a single, comprehensive path. It upholds meditative disciplines such as śamatha–vipaśyanā and shikan (“stopping and seeing”), aiming at direct insight into the true nature of mind and phenomena. Alongside meditation, it incorporates esoteric rituals, mantras, and mandala-related practices, as well as liturgical chanting, recitation of the Lotus Sūtra, and Pure Land nembutsu. Ethical precepts and monastic discipline are also emphasized, so that contemplative insight, ritual expression, and moral conduct mutually reinforce one another.

Historically, Tendai became a fertile training ground for many influential Japanese Buddhist figures, and several later traditions, including Pure Land, Zen, and Nichiren, trace important aspects of their formation to this milieu. Its attempt to hold together diverse teachings—Zen-style meditation, esoteric ritual, Pure Land devotion, and rigorous precepts—under the unifying vision of the Lotus Sūtra gives it a distinctive character among Buddhist schools. Tendai may thus be seen as an ambitious effort to honor the full breadth of the Buddhist heritage, while affirming that all these varied practices ultimately converge on the realization of universal Buddhahood.