Theobald Rehbaum (17 August 1835 – 2 March 1918) was a German violinist, librettist and composer, especially of operas.
Born in Berlin, Rehbaum grew up there and sang as a boy in the Royal Domchor.
He studied violin and composition with Friedrich Kiel, and composition also with Hubertus Rios.
Rehbaum composed several operas and choral works, but was more successful as a librettist, writing librettos for Bernhard Scholz.
He also wrote a Bratschenschule zum Selbstunterricht für Violinisten (viola method for self-instruction for violinists) and an autobiography titled Erlebtes und Erstrebtes.