The Katha Upanishad (Devanagari: कठ उपनिषद्) (Kaṭhopaniṣad, also Kāṭhaka), also titled "Death as Teacher", is one of the mukhya ("primary") Upanishads. It is associated with the Cāraka-Kaṭha school of the Black Yajurveda, and is grouped with the Sutra period of Vedic Sanskrit. It is a middle Upanishad. It consists of two chapters (adhyāyas), each divided into three sections (vallis) that contain between 15 and 29 verses (ślokas) apiece. The Katha has some passages in common with the Gita. According to modern scholars, it propounds a dualistic philosophy.
Katha may be the most widely known amongst all the Upanishads; its early Persian translations first found their way into Europe. Max Müller translated it 1879, Edwin Arnold rendered it in verse, as "The Secret of Death" and Ralph Waldo Emerson gave the central story at the end of his essay, Immortality. Central to the text is the story of Nachiketa, son of sage Vajasravasa, and his encounter with Yama, Hindu God of death.