Kamsa (Sanskrit: कंस, romanized: Kaṃsa) was the tyrant ruler of the Vrishni kingdom, with its capital at Mathura. He is variously described in Hindu literature as either a human or an asura; The Puranas describe him as an asura, while the Harivamśa describes him as an asura reborn in the body of a man. His royal house was called Bhoja; thus, another of his names was Bhojapati. He was the cousin of Devaki, the mother of the deity Krishna; Krishna ultimately fulfilled a prophecy by slaying Kamsa.

Kamsa was born to King Ugrasena and Queen Padmavati. However, out of ambition, and upon the advice of his personal confidantes, Banasura and Narakasura, Kamsa decided to overthrow his father, and install himself as the King of Mathura. Therefore, upon the guidance of another advisor, Chanura, Kamsa decided to marry Asti and Prapti, the daughters of Jarasandha, King of Magadha.

After a heavenly voice prophesied that Devaki's eighth son would slay him, Kamsa imprisoned Devaki and her husband Vasudeva, and killed all of their children; however, just before the birth of the seventh child of Devaki and Vasudeva, Vishnu ordered the goddess Mahamaya to transfer the child from the womb of Devaki to that of Rohini, another wife of Vasudeva. Soon, Rohini gave birth to Devaki's seventh son, named Balarama. The eighth son, Krishna, an avatar of Vishnu, was transported to the village of Gokula, where he was raised in the care of Nanda, the head of the cowherds. Learning of his birth, Kamsa sent a host of asuras to kill the child Krishna, but Krishna killed every one of them. Finally, Krishna arrived in Mathura and slew his uncle, Kamsa.