Sharanga is the bow of the Hindu God Vishnu. Other weapons of Vishnu include the Sudarshana Chakra, the Narayanastra, the Vaishnavastra, the Kaumodaki mace, Nandaka sword.
This bow was crafted by Viswakarma, the Cosmic architect and maker of weapons, along with the Pinaka, the bow of Lord Shiva. Once, Brahma wanted to know who was a better archer, Vishnu or Shiva. Brahma created a quarrel between the two, which led to a terrible duel. The impact of their fight was such that the balance of the entire universe was disturbed. But soon Vishnu was able to paralyze Shiva with his arrows. All the Devas led by Brahma himself begged them to stop, declaring Vishnu the winner as he was able to stun Shiva. Enraged, Shiva gave his Pinaka bow to a king, who was an ancestor of King Janaka, the father of Sita. Vishnu too decided to do the same, and gave his bow to the sage Richika. In time, Sharanga came into the possession of Parashurama, the sixth avatar of Vishnu and Richika's grandson. Parashurama gave it to Rama, the next incarnation of Vishnu after fulfilling his life's mission. Rama used it and gave to Varuna, the lord of the hydrosphere. In the Mahabharata, Varuna gives it to Krishna(eight avatar of Vishnu) during the Khandava-dahana. Just before his death, Krishna returned it to Varuna by throwing it back into the ocean, Varuna's domain.
Sharanga appears during a duel between Lord Krishna, the eighth incarnation of Lord Vishnu, and Shalva, the demon of mystical powers. Shalva strikes Krishna's left arm causing him to drop Sharanga. Later, Krishna severs Shalva's head with Sudarshana Chakra.