Eileen Edna Le Poer Power (married name Postan) was born on January 9, 1889, in Altrincham, Cheshire, England.

She was a British economic historian, medievalist, educator, and author. She was educated at Oxford High School for Girls and Girton College, Cambridge (1907-1910). In 1910, she was awarded the Gilchrist research fellowship and studied at the University of Paris and the École des Chartes. On her return to Britain, she was awarded the Shaw research studentship at the London School of Economics (1911–1913), where she studied medieval women. Power became Director of Studies in History at Girton College, University of Cambridge (1913–1921), Lecturer in Political Science at the London School of Economics (1921–1924), and Reader of the University of London (1924–1931). Power visited India, China and Japan after she became the first woman to be was awarded the Albert Kahn travelling scholarship in 1920. In 1931, she became the second woman to be appointed to the Chair of Economic History at the London School of Economics. She was the author of many books, e.g., "Medieval English Nunneries" (1922) and "Medieval People" (1924). Several of her lectures were edited by her husband, Michael M. Postan, and published as "Medieval Women" in 1975.

In 1937, she married Mikhail Moissey Postan (1898–1981). She died on August 8, 1940, in London, England.