Otto Wallach (27 March 1847 - 26 February 1931) was a German chemist and recipient of the 1910 Nobel prize in Chemistry for his work on alicyclic compounds.

In 1867 he started studying chemistry at the University of Göttingen, where at this time Friedrich Wöhler was head of organic chemistry.
Wallach received his Doctoral degree from the University of Göttingen in 1869, and worked as a Professor in the University of Bonn (1870–1889) and the University of Göttingen (1889–1915). Wallach died at Göttingen.
In 1909, He wrote a book about the chemistry of terpenes, "Terpene und Campher".