William Henry Walenn (7 January 1828 – 20 September 1896) was born in London and was trained as an engineer at the works of Messrs. Cottam, and received part of his education at University College, London, where he studied mathematics under Augustus De Morgan. He became a Fellow of the Chemical Society in 1866, and of the Institute of Chemistry soon after its establishment. He was also a member of the Physical Society of London.