William Carmichael M'Intosh FRSE FRS FLS (also spelt McIntosh; 10 October 1838, St Andrews – 1 April 1931, St Andrews) was a Scottish physician and marine zoologist. He served as president of the Ray Society, as vice-president of the Royal Society of Edinburgh (1927–30), and was awarded the Neill Prize (1865-8).
McIntosh lived and worked as a psychiatric doctor in Perthshire, and was Director of the Perthshire District Asylum at Murthly for 18 years, but later became a renowned botanist and marine biologist. He travelled on HMS Challenger during the Challenger expedition of 1872 to 1876. He was Professor of Natural History at St Andrews University from 1882 to 1917, succeeded by D'Arcy Wentworth Thompson. He was also Director of the University Museum and was the first director of the University's Gatty Marine Laboratory (founded 1896). McIntosh was also a Fellow of the Linnean Society of London, a Fellow of the Royal Society of Edinburgh, and a Corresponding Member of the Zoological Society. He was elected a Fellow of the Royal Society in 1877, and was awarded the Royal Society's Royal Medal in 1899: "For his important monographs on British marine zoology and on the fishing industries." He was awarded the Linnean Medal in 1924.
- Waterston, Charles D; Macmillan Shearer, A (July 2006). Former Fellows of the Royal Society of Edinburgh 1783-2002: Biographical Index II. Edinburgh: The Royal Society of Edinburgh. ISBN 978-0-902198-84-5. Retrieved 30 December 2011.
- "Obituary Notices". Proceedings of the Royal Society B: Biological Sciences 110 (768): i–c. 1932. doi:10.1098/rspb.1932.0031.
- Entry at the Complete Dictionary of Scientific Biography
- Entry for McIntosh in the Royal Society's Library and Archive catalogue's details of Fellows (accessed 23 April 2008)
- William Carmichael McIntosh, picture from the Natural History Museum
- William Carmichael McIntosh, from the University of St Andrews Library Photographic Archive
- William Carmichael McIntosh (1838-1931), manuscript collection at the University of St Andrews