Frances Elizabeth Somerville Alexander (née Caldwell; 13 December 1908 – 15 October 1958) was a British geologist, academic, and physicist, whose wartime work with radar and radio led to early developments in radio astronomy and whose post-war work on the geology of Singapore is considered a significant foundation to contemporary research. Alexander earned her PhD from Newnham College, Cambridge, and worked in Radio Direction Finding at Singapore Naval Base from 1938 to 1941. In January 1941, unable to return to Singapore from New Zealand, she became Head of Operations Research in New Zealand's Radio Development Lab, Wellington.