Edith Margaret Robertson Ditmas (1896 – 28 February 1986) was an English archivist, historian and writer.

[2] She was an influential official of the British Association of Special Libraries and Information Bureaux, whose journal she edited.

As general secretary of what became the Association for Information Management (ASLIB) in 1946–1950, she called strongly at the Empire Scientific Conference for "a combination of government encouragement and private initiative" in developing specialized information services.

This circulated in typescript and was published posthumously in 2009, with addenda of information on subsequent archaeological research and of early maps.

[5] The one surviving picture of Ditmas was taken on a Women's Institute outing, the WI being one of her abiding interests.