Sri Agasthiyar (also transliterated as Agathiar, Agasthiar, Agastyar, Agasti, Agastiar) is a legendary Vedic Rishi (sage). It is believed that sage Agasthiyar was instrumental in spreading the Vedic religion in southern India.
Agastya is also recognized as one of Seven Great Sages (Saptarishis). Sage Agasthiyar has also contributed immensely to the four Vedas. These mantras were revealed to Sage Agasthiyar by the Brahman (Supreme Being) itself.
Agasthiyar is also the leader of all Siddhas. He is also called Kurumuni, meaning short (kuru) saint (muni). His contributions are manily in the fields of Medicine (Siddha) and Astrology - especially Nadi Jodhidam (Jos(i)yam or Jothisyam). He is said to have lived for over 5000 years, and that one of his medicinal preparations, Boopathi Kuligai, is so powerful that it can even bring the dead back to life. Two of his students and disciples were Therayar and Tholkappiar. He is also considered to be the guru of many other Siddhars.
The Lalitha sahasranama, which describes the 1000 names of the mother Goddess (Known commonly as Gowri, Parvati or Durga), was first revealed to the world when Hayagriva, an Avatar of Vishnu, taught the same to Agasthiyar. Agasthiyar is said to have composed the Aditya Hridayam, a hymn on Sun God (Surya), and taught the same to Rama just before the war between Rama and Ravana.
He is also believed to be the author of Agastya Samhita. The word is also written as Agasti and Agathiyar. A-ga means a mountain, and Asti means thrower. Agastya is also the Indian astronomical name of the star of Canopus, is said to be the 'cleanser of waters', since its rising coincides with the calming of the waters of the Indian Ocean.
He was son of Pulasthya, son of Brahma. Siddhar were spiritual adepts who possessed the ashta siddhis, or the eight supernatural powers. Sage Agathiyar is considered the guru of all Siddhars, and the Siddha medicine system is believed to have been handed over to him by Lord Muruga, son of the Hindu God Lord Shiva and Goddess Parvathi.Siddhars are the followers of Lord Shiva.
Agathiyar is the first Siddhar. His disciples and other siddhars contributed thousands of texts on Siddhar litratures, including medicine and form the propounders of the system in this world. He is considered as the Father of Tamil literature and compiled the first Tamil grammar called Agathiyam. It is believed that he has lived in the 6th or 7th century B.C and specialized in language, alchemy, medicine and spirituality (yogam and gnanam). There are 96 books in the name of Agathiyar.
However, some Tamil researchers say that Agastya mentioned in Vedas and Agathiyar mentioned in Tamil texts could be two different characters. In Tamil language the term 'Agam' means inside and 'iyar' means belong. One who belong inside (soul) is the Tamil meaning for Agathiyar.