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 1945, Alexander correctly interpreted that anomalous radar signals picked up on Norfolk Island were caused by the sun.

She graduated with First-class honours in 1931, then received a PhD in geology for a thesis on Aymestry Limestone, under the supervision of Owen Thomas Jones.

When her husband took the post of Professor of Physics at Raffles College in Singapore, Elizabeth Alexander travelled there and began a study into the effects of weathering in the tropics.

[10] Whilst in New Zealand, Alexander became Senior Physicist and Head of the Operational Research Section of the Radio Development Laboratory in Wellington in 1942, where she remained until 1945.

[4] Whilst Alexander worked in New Zealand, her husband had continued as Scientific Adviser to the Armed Forces, moving to help out at Singapore General Hospital when Raffles College was on the front line.

[19] She sought to restart her work on tropical weathering, however the lab in her house had been destroyed and, during road building, the top of a hill that she had used for triangulation had been removed thus making it impossible to locate her buried experimental samples.

[22] Alexander was also responsible for introducing the name "Murai Schist" to refer to a part of the Jurong Formation, and created the first documented collection of fossils in the area of the Ayer Chawan Facies.

After the move, a member of staff at Raffles Museum managed to locate one of Alexander's experimental samples of buried rocks, and arranged for it to be sent to Rothamsted Research Station near London so that she could examine it during annual leave.