Dame Elsie Marjorie Williamson, DBE (30 July 1913, Wakefield, Yorkshire, England — 12 August 2002Lower Raydon, Suffolk) was a British academic, educator, physicist and university administrator.
The only child of middle-aged parents she attended Wakefield Girls' High School and went up to read physics at Royal Holloway College, University of London (RHC) in 1932, graduating in 1936.
She stayed at Royal Holloway as a Demonstrator in physics, before spending the Second World War years lecturing at the University College of Wales in Aberystwyth (now Aberystwyth University).
In 1945, she moved to Bedford College, London, as a lecturer in physics. She spent 10 years there, gaining her PhD and working in the fields of relativity, quantum mechanics and electromagnetic theory. At Bedford she was involved not only in the physics department, but took a great interest in the administration of the college.
In 1955 she was appointed Principal of St Mary's College, Durham.
She was invited to become Principal of Royal Holloway College, University of London, (RHC) in 1962 following the resignation of Dr Edith Clara Batho. Before Williamson became Principal, RHC admitted only women as undergraduates and offered a relatively restricted number of courses. Men were only admitted as postgraduates after 1945. Because of this, and its situation in the outer London suburb of Englefield Green, Surrey, the RHC was seen as something of a backwater.