William Ecroyd Farrer (28 February 1861 – 17 August 1924) was an English historian and genealogist.
He was educated at Rugby School, then briefly joined the family's worsted manufacturing business.
Farrer's interest in Lancashire and Yorkshire genealogy led into his research on wider local history.
He contributed much to local societies and their journals as he began his work on History of the Parish of North Meols.
With John Brownbill as co-editor, he published eight volumes of the Victoria History of the County of Lancaster between 1906 and 1914.