Kaustubha (Sanskrit: कौस्तुभ, romanized: Kaustubha, lit. 'crest jewel') is a divine ruby or ratnam (gem) in Hindu mythology. This gem is in the possession of Vishnu, granting him the epithet of Kaustubhadhari. It is believed in Hindu scriptures to be the most magnificent ratnam in all of creation, at the time of the churning of the ocean, and acts as a symbol of divine authority.