William Mercer

William Mercer (9 May 1905 – March 1965) was an English professional rugby league footballer who played in the 1920s and 1930s. He played at representative level for England and Lancashire, and at club level for St. Helens (captain), as a or .

Representative honours Mercer won a cap for England while at St. Helens in the 19–35 defeat by Other Nationalities at Thrum Hall, Halifax on Monday 7 April 1930.

Mercer made his début for Lancashire in the 15–7 victory over Cumberland at Whitehaven on Tuesday 29 October 1929, alongside fellow St. Helens player Alf Ellaby who scored three tries, Mercer had two further victories alongside Alf Ellaby, against Yorkshire and Glamorgan and Monmouthshire as Lancashire won the County Championship.