Theodor Weyl (8 January 1851 – 6 June 1913) was a German chemist and hygienist born in Berlin.
He studied at the universities of Heidelberg, Berlin and Strasbourg, earning his doctorate in 1872 with a dissertation on animal and plant proteins.
During his tenure at Erlangen he spent the winter of 1880–81 performing research on the electric organs of rays at the Stazione Zoologica Anton Dohrn in Naples.
With Heinrich Houben (1875–1940), the "Houben-Weyl Methods of Organic Chemistry" is named, a massive reference work that by 2003 had grown to 162 volumes.
He made contributions in the field environmental chemistry, being deeply concerned with issues involving public health.