The Platform Sutra of the Sixth Patriarch (Chinese: 六祖壇經; pinyin: Liùzǔ Tánjīng or simply: 壇經 Tánjīng) is a Chan Buddhist scripture that was composed in China during the 8th to 13th century. The "platform" (施法壇) refers to the podium on which a Buddhist teacher speaks. It is a repository of early Chan teachings, centering on the notion of the Buddha-nature, which is "only made invisible to ordinary humans by their illusions." Notably, In Chan Buddhism it is the only Chinese Buddhist text that is explicitly referred to as a "Sutra," emphasizing its central importance in the canon.

The text centers on the teachings and stories ascribed to the sixth Chan patriarch Huineng. It contains the well-known story of the contest for the succession of Hongren (enlightenment by the non-abiding), and discourses and dialogues attributed to Huineng.

The text attributes its recollection to Fa-hai, but was probably written, or redacted, within the so-called Oxhead school, which existed along with the East Mountain School and Shenhui's Southern School. The text attempts to reconcile the so-called Northern School with its alleged gradual enlightenment teachings, and the so-called Southern School with its alleged sudden enlightenment teachings. In effect, the text incorporates the "rhetorical purity" which originated with Shenhui's attack on Shenxiu, while effectively "writing him out of the story".

The Platform Sutra underwent various redactions. Though its recollection has been attributed to Fa-hai, a student of Huineng, its origins are not clear:

The early development of the Platform Sutra is shrouded in the mists of time, and we will probably never know much for certain about it. The Dunhuang Manuscripts version of the text, the earliest complete edition we have, is almost certainly a product of a long evolution with elements coming together from several different Chan groups with different agendas, as the uneven character of the text and its internal inconsistencies attest.

The Dunhuang versions are the oldest texts available, with the full title Southern School's Sudden Doctrine, Supreme Mahayana Great Perfection of Wisdom: The Platform Sutra as Delivered by the Sixth Patriarch Huineng at the Dafan Temple in Shao Prefecture Chinese: 南宗頓教最上大乘摩訶般若波羅蜜經：六祖惠能大師於韶州大梵寺施法壇經, subtitled, “one roll, recorded by the spreader of the Dharma, the disciple Fahai, who at the same time received the Precepts of Formlessness” (一卷，兼受無相戒弘法弟子法海集記).

Two copies dated to between 830 and 860 have been found in the Mogao Caves in Dunhuang. Both are thought to be based on an edition from about 780. The finds at Dunhuang have been very important for the historical understanding of Zen:

Scholarship on early Chan was transformed after the discovery in the beginning of the twentieth century of a number of texts relating to the early Chan movement in the cave library at Dunhuang, which also contained an early version of the Platform Sutra.