Bali, also known as Mahabali (Great Bali) was an Asura. He was a benevolent demon king and ruled over all earth and the underworld. He also claimed parts of the heavens as his realm. He was defeated by the god Vishnu in his form of Vamana the dwarf. He was a grandson of Prahlada and thus great-grandson of Hiranyakashipu.
Vamana went to see the king Bali. He asked for a piece of land which could cover three steps. Bali agreed. Vamana took one step and covered the heavens. He took another, covering Earth and the last step covered the underworld. Thus was Mahabali defeated and sent to the underworld.