Otto Mahler (18 June 1873 – 6 February 1895) was a Bohemian-Austrian musician and composer who died by suicide at the age of 21. The twelfth child of Bernard and Marie Mahler, Otto was born in Jihlava and resembled his elder brother Gustav Mahler in displaying a special talent for music at an early age. Otto Mahler's music remains unpublished and is apparently uncatalogued. No recent performances are known; indeed, the very survival of the scores is currently uncertain.