Amsha Avatar is the part manifestation or half avatar of Vishnu or Shiva in Hinduism. It is distinguished from the full manifestation (purnavatara). Some of the Puranas describe twenty two and twenty four manifestations of Bhagavan Vishnu, but are important – Matsya, Kurma, Varaha, Narasimha, Vamana, Parashurama, Rama, Balarama, Krishna and Kalki (which is yet to come). Even among these ten manifestations, Narasimha, Rama and Krishna are considered as full manifestations in which all the divine characteristics are present. The rest are Amshavataras. Besides, sages, gods and the valiant sons of Manu are all Amsha Avatars of Bhagwan Vishnu.
In the Balakanda of Ramayana, when Bhagavan Vishnu descended as Rama, the different gods are referred to as having descended as monkeys and bears. Similarly, in the Adi Parva of the Mahabharata, the Pandavas, Kauravas and others are described as Amhavataras of the gods. The scriptures declare that the entire universe consisting of movable and immovable objects is an infinitesimal part of Bhagavan Vishnu.
The Bhagavad Gita referring to this concept of the manifestation of Vishnu, states that whenever there is decline in righteousness, Bhagavan descends to the earth in order, to remove unrighteousness and injustice and that he appears millennium after millennium, in order to protect the pious and destroy the wicked.
The presence of all the divine qualities characterizes an integral manifestation; in an amshavatara only some of the divine qualities are present.
Among the sixteen kalas (powers) of a manifestation, the five – vision, hearing, smell, taste and touch – are shared by God with all animate including human beings and animals; the other four – relating to mind, heart intelligence and state of existence – are shared by Bhagavan only with human beings. The rest – grace, special grace, power to create, power to support, power to destroy, the assumption of a form and the assumption of a name – are the characteristics of an integral manifestation alone. Many are deemed to be Amsha Avatar because all the sixteen characteristics in full manifestations are not found in them.
Vishnu Purana states that Vishnu made amsha avatars in the different manvantara periods: Yajna in the first manvantara as son of Akuti, Ajita in the svarocisha manvantara as son of Tusita, Satya in the auttama manavantara as son of Satya, Hari in the tamasa manvantara as son of Harya, Manasa in the raivatara manvantara as son of Sambhuti, Vaikunta in the cakusha manvantara as son of Vaikunta and Vamana in the vaivasvata manvantara as the son of Kashyapa and Aditi. It concludes that Vishnu has pervaded the entire universe by means of his innate power.
Many realized souls in the recent past such as Shankara Bhagavatpada, Ramakrishna Paramahamsa and Bhagavan Ramana Maharshi are cited sometimes as examples of Amsha Avatara.