The Upanishads have been translated into various languages including Persian, Italian, Urdu, French, Latin, German, English, fDutch, Polish, Japanese, Spanish and Russian. The Moghul Emperor Akbar's reign (1556–1586) saw the first translations of the Upanishads into Persian, and his great-grandson, Dara Shikoh, produced a collection called Sirr-e-Akbar (The Greatest Mysteries) in 1657, with the help of Sanskrit Pandits of Varanasi. Its introduction stated that the Upanishads constitute the Qur'an's "Kitab al-maknun" or hidden book. But Akbar's and Sikoh's translations remained unnoticed in the Western world until 1775.
Abraham Hyacinthe Anquetil-Duperron, a French Orientalist who had lived in India between 1755 and 1761, received a manuscript of the Upanishads in 1775 from M. Gentil, and translated it into French and Latin, publishing the Latin translation in two volumes in 1802–1804 as Oupneck'hat. The French translation was never published.
The first English translation of the Aitareya Upanishad was made by Colebrooke, in 1805 and the first English translation of the Kena Upanishad was made by Rammohun Roy in 1816. Colebrooke was aware of 170 Upanishads. Sadhale's catalog from 1985, the Upaniṣad-vākya-mahā-kośa lists 223 Upanishads.
The first German translation appeared in 1832 and Roer's English version appeared in 1853. However, Max Mueller's 1879 and 1884 editions were the first systematic English treatment to include the 12 Principal Upanishads. After this, the Upanishads were rapidly translated into Dutch, Polish, Japanese and Russian.