Alexander Crichton Mitchell FRSE (1 July 1864 – 15 April 1952), named in some sources as Arthur Crichton Mitchell, was a Scottish physicist with a special interest in geomagnetics who worked for many years in India as a professor and head of a meteorological observatory before returning to Scotland. He then worked with the Royal Navy to devise a system, known as an anti-submarine indicator loop, for detecting submarines by detecting currents induced in a loop of wire on the sea floor.