|Part of a series on|
Avatsara is the main poet of Sukta 44 of the Fifth Mandala of the Rig veda which hymn addressed to the Rigvedic deities, the Visvedevas. He is more known for the set of eight hymns of four mantras each appearing in the Rig Veda viz. Suktas IX.53 to IX.60, and also in the Samaveda (SV.757, SV.1717).  He was the Hotr of the gods. He had delighted Agni by the six-syllable oblation – O Agni, enjoy the oblation, and was set-free. According to Satyasadha (21.3.13), the parvaras of Kashyaps consist of three rishi – ancestors: – Kashyap, Avatsara and Naidhruva.  There are eight notable rishis belonging to the Kashyap family – Kashyap, Avatsara, Nidhurva, Rebha, Devala, Asita, Bhutamsa and Vivrha; two unnamed sons of Rebha were also authors of Rigvedic hymns.
As Vedic Rishi
Avatsara was the son of Rishi Kashyap who was later than Rishi Vamadeva but earlier than Rishi Atri. The word, Avata, denotes an artificially dug up water-source or an artificial well.  Avatsara Prasravana, like his father Kashyap, was a Rishi of the Rig Veda. His name first appears in Sukta 44 of the Fifth Mandala.
He is more known for the Suktas 53 to 60 of the Ninth Mandala; these Suktas contain four mantras each, all composed in the Gayatri Metre. In the Rig Veda, he addresses Ishvara as अद्रिवः, the fully armed and endowed with many subtle and fine divine powers and destroyer of all evil forces (RV.IX.53.1). He then addresses Ishvara as शुक्रम् which means the purifier or the pure, brilliant as the Sun.
His name appears in the Yajurveda, (Y.V.III.i & III.xviii) where he prays to Agni, and in the Aitareya Brahmana and the Kausitaki Brahmana. From the verses of the Aitareya Brahmana (A.B. ii.24) and Kausitaki Brahmana (K.B.viii.6), both pertaining to the Sacrifice of the Five Oblations, it is learnt that Avatsara had reached the home of Agni and had conquered the highest world.
- अति वारन्यवमानो असिष्यद्त्कल्शां अभि धावति |
- इन्द्रस्य हार्द्याविशन् ||
that the Lord, in the form of knowledge and consciousness, resides in the cleansed mind and heart of the learned people and in the mind and heart of all those who know the Lord fully without being aware of knowing Him. 
Apart from Kashyap Marichi there appears to have been a second Kashyap who was the father of Avatsara, Narada and Arundhati, the wife of Rishi Vasistha and it was this second Kashyap who was one of the Sapta Rishis. According to the Vishnu Purana, Avatsara or Vatsara was the son of Kashyap, the son of Marichi. And, according to the list of Rishis provided by the Matsya Purana, Kashyap had two sons – Avatsara and Asita; Nidhruva and Rebha were Avatsara’s son. But this list is doubted; the genealogy otherwise gives three groups among the Kashyaps, the Sandliyas, Naidhruvas and Raibhyas.
From Book IV Chapter VIII of the Srimad Bhagvatam it is learnt though Lord Maitreya that Dhruva, the son of Uttanapada through Suruti, and the grandson of Svyambhuva Manu, had by his first wife Brahmi, two sons,Vatsara and Kalmavatsara or Kalpa.
- Shrikant G.Talageri. The Rig Veda: A Historical Analysis. Aditya Prakashan.
- All Four Vedas. Agniveer. pp. 124–134, 326,409–417, 734.
- Arthur Barriedale Keith. Rig Veda Brahmanas:The Aitareya and Kausitaki Brahmanas of the Rig Veda. Motilal Banarsidass. p. 419.
- Dhundiraja Ganesa. Sarautakosah:Encyclopaedia of Vedic Sacrificial Rituals. p. 1016.
- Purushottam Lal Bhargava. India in the Vedic Age. D.K.Print World. p. 221.
- Islamkotob. Rig Veda A Historical Analysis. Islamic Books. p. 102.
- Arthur Anthony Macdonell. Vedic Index of Names and Subjects Vol.1. Motilal Banarsidass. pp. 39–40.
- Jayantanuja Bandopadhayaya. Class and Religion in Ancient India. Anthem Press. p. 13.
- Ravinder Kumar Soni. The Illumination of Knowledge. GBD Books. pp. 246–247.
- Agniveer. All Four Vedas. Agniveer. p. 46.
- Arthur Barriedale Keith. Rig Veda Brahmanas:The Aitareya and Kausitaki Brahmanas of the Rig Veda. Motilal Banarsidass. p. 153.
- Ravinder Kumar Soni. The Illumination of Knowledge. GBD Books. pp. 247–248.
- Sita Nath Pradhan. Chronology of Ancient India. Bhartiya Publishing House. p. 90.
- Praci-jyoti. Kurukshetra University.
- Ganga Ram Garg. Encyclopaedia of the Hindu World Vol.3. Concept Publishing Company. p. 839.
- Fitzedward Hall. The Vishnu Purana. p. 232.
- F.E.Pargiter. Ancient Indian Historical Tradition. Motilal Banarsidass. p. 231.
- Francis Wilford. On the chronology of the Hindus Asiatic Researches Vol. 5. New Jersey College Library. p. 253.
- Swami Venkatesananda. The Concise Srimad Bhagvatam. Suny Press. p. 86,90.
- The Early Brahmanical System of Gotra and Pravara. Cambridge University Press. p. 36.