Nathamuni was a Vaishnava theologian who collected and compiled the Nalayira Divya Prabandham. Considered the first of Sri Vaishnava āchāryās, Nathamuni is also the author of Yogarahasya, and Nyāyatattva.
Nathamuni (Named by parents as Aranganathan) is generally considered to have been born in 824 AD and to have died in 924 AD. An alternative view is that he was born in 582 AD and died in 922 AD. Yet another view is that Nathamuni was born at Viranarayana Puram sometime shortly after 907 AD and flourished in the 10th century. Though there is difficulty in fixing Nathamuni's date of birth and age, he is considered to have lived during the lifetime of Madhurakavi Alvar's Parampara. That Nathamuni was in contact with Nammalvar is attested by the Guru-paramparā, Divya sūri charita, and Prappannāmŗta. The Prappannāmŗta also attests that Nathamuni was born in the village Viranarayana. Viranarayana is today generally identified as Kattumannarkoil. Nathamuni is said to have died at Gangaikonda Cholapuram. His father's name was Iśvara Bhaṭṭa and his son's name was Iśvaramuni. His grandson was Yamunacharya.
It is believed that his other names were Sadamarsana Kula Tilakar and Sottai Kulaththu Arasar.
He spent time travelling in north India. He came to know about Nalayira Divya Prabhandam, but he heard only 10 hymns. He wanted the rest. He recited 12000 times, Kanninun Siruthambu, a poem in praise of Nammazhwar. Nammazhwar appeared and gave the 4000 hymns(Nalayira Divya Prabhandam). He was the one who brought back the 4000 hymns. In addition to teaching the hymns to his two nephews at Srirangam, he introduced them into the Srirangam Temple Service at the Sri Ranganathaswamy Temple, Srirangam where he was the Temple Administrator.
He is thought to be the originator of the Araiyar Sevai. The modern days 'Thathachariars' a sect of Tamil Nadu Iyengars are the descendants of this Aacharya, housing a lot of great people in Sri Vaishnavism ranging from Sri Alavandar ( Sri Yamunacharya), Sri Thirumalai Nambikal, Sri Emberumanar, Sri Kurugesar, Sri Panchamatha bandhana Thatha Desikan, Sri Kotikannikadhana Sri Lakshmi Kumara Thathachariar. The disciples of this Aacharya known as 'Melayagaththalwan' and 'Keelayagaththalwan' families propagated this Aarayar Sampradhayam.