Agattiyam (Tamil: அகத்தியம் ), also spelled as Akattiyam, according to Tamil tradition, was the earliest book on Tamil grammar. It is a non-extant text, traditionally believed to have been compiled and taught in the First Sangam, (circa 300 BCE) by Agattiyar (Agastya) to twelve students. Agastya is one of the seven revered rishi of Vedic literature, mentioned in the Rigveda. A few surviving verses of Akattiyam are said to be quoted in medieval commentaries.
Agastya, in medieval commentaries of Tamil Hindu scholars, is variously credited with either creating the Tamil language or learning it from the god Shiva. In contrast, according to medieval era Tamil Buddhist scholars, the sage learned Tamil from Avalokita. These legends are mentioned in Akitti Jataka and in Tamil Buddhist epics. There is no direct mention of the sage's name, or Agattiyam text, in Tolkappiyam or the bardic poetry of the Sangam literature.
