Nanyue Huisi (Chinese: 南嶽慧思, 515-577), was an eminent Chinese Buddhist monk, traditionally regarded as the third patriarch of the Tiantai school. According to Sasaki, Huisi "was the leading authority on the Lotus Sutra of his time."
The earliest sources on Huisi´s life are the "Vow Established by the Great Dhyana Master Huisi from Southern Peak", a work attributed to Huisi,Dàoxuān´s hagiography in the "Continued Biographies of Eminent Monks" (續高僧傳 Xù gāosēng zhuàn) and in his "Catalogue of [Buddhist] Works in the Imperial Collection of the Great Tang".
Born with the surname Li (李) in Wujin 武津 (Shangcai 上蔡, Henan 河南) in 515 CE, Huisi left home to join the monastic order at fourteen. By the age of nineteen, he undertook the full monastic precepts, thus becoming a fully ordained monk. Then he began visiting meditation masters in northern Henan.
He joined the community of Huiwen, who, according to Tiantai tradition, taught meditation techniques of the Great Perfection of Wisdom Treatise, a work purportedly written by Nagarjuna. Dàoxuān (597-667) reports that after a ninety-day retreat under Huiwen´s guidance, Huisi attained sudden enlightenment while leaning against a wall: "Within an instant of thought he attained the dharma-gate of the lotus samadhi". Guanding (561-632) writes: "The dharma-gates of both the Lesser Vehicle and Great Vehicle radiantly burst forth [for him]." Subsequently, Huisi began to give public lectures and to teach samadhi to an increasing number of disciples. However persecution by opposing monks, who ultimately tried to kill him, forced him to flee to south China in 552.
From 553-568 he lived and taught in Guangzhou. Among his disciples were several gifted monks like Zhiyi, who studied on Mt. Dasu under Huisi from 560 to 567. Zhiyi would become the fourth patriarch in the Tiantai lineage.Dàoxuān states that Huisi went to Mount Nan Yue in 568, where he founded the Yuquan Temple and trained his disciples.
Huisi taught two different forms of the lotus samadhi, the "practice devoid of characteristics", or the practice of ease and bliss, is based on the fourteenth chapter of the Lotus Sutra. Huisi explains, "While in the very midst of phenomena [the practitioner discerns that] mental characteristics are quiescent and extinguished and ultimately do not arise. (...) He is constantly immersed in all the profound and wonderful dhyana absorptions because in all activities - walking, standing, sitting, lying down, eating or speaking - his mind is always settled [in samadhi]."