mountain chain in eastern Zhejiang (Chekiang) province, eastern China. Tiantai is also the name of a mountain in the chain. The range forms the northeastern extension of the great Xianxia Mountains in southern Zhejiang, which form the watershed between the Ling River and the Ou River, draining to the east coast of Zhejiang, and the Yin River, the Cao'e River, and rivers of the Qiantang River system, draining to the west and eventually to the north coast of the province. The mountains are rugged, with individual peaks reaching 3,300 to 4,000 feet (1,000 to 1,200 metres). The mountain known as Tiantai (“Heavenly Terrace”) comprises a series of peaks—Tongbai, Foulong, Chicheng, and, the highest, Huading, which reaches 3,589 feet (1,094 metres).

From a very early period the Tiantai mountain chain was considered holy, and in ancient times it was associated with Daoism. Many well-known Daoist adepts and masters lived there until the 11th and 12th centuries. Its fame, however, is associated not with Daoism but with Buddhism. According to tradition, the first Buddhist community was founded there in 238–251, but the renown of Tiantai began when the monk Zhiyi settled there in 576. When the Sui (Sui dynasty) dynasty (581–618) unified China in 589, Zhiyi played an important role in giving religious sanction to the new regime and was greatly honoured by the Sui emperor. After Zhiyi's death in 597, his disciples, under imperial patronage, made Tiantai a major cult centre. The best-known temples established there were the Guoqing, Dazi, Dianfeng, Huoguo, Wannian Bo'er, and Gaoming. Eventually there were 72 major temples as well as a great number of cloisters and shrines on the mountain, and it became a major centre of pilgrimage for both Chinese and Japanese Buddhists. It also gave its name to one of the major schools of Buddhist teaching, Tiantai, perhaps better known under its Japanese name of Tendai.

Many of the temples still remain, although the influence of the Tiantai school in Chinese Buddhism did not survive the 13th century. A good deal of building continued in the 17th and 18th centuries, and in the 17th century in particular the Tiantai area produced a number of prominent Buddhist scholars.