John Theodore Merz (30 March 1840 – 21 March 1922) was a German British chemist, historian and industrialist. Merz was born in Manchester, England and educated at University of Giessen, Göttingen, Heidelberg, and Bonn universities. Merz was vice-chairman of the Newcastle-upon-Tyne Electric Supply Company, which he founded in 1889. He was chairman of the Tyneside Tramways and Tramroads Company and a member of the senate of Durham University. In 1906, he was awarded an LLD degree from the University of Aberdeen. Merz was buried in Elswick, St John's Cemetery.