Alphonsus Josephus de Ridder (7 May 1882 – 31 May 1960), was a Belgian writer and poet who wrote under the pseudonym Willem Elsschot. One of the most prominent Flemish author, his most famous work, Cheese (1933) is the most translated Flemish-language novel of all time

Elsschot began writing poetry in 1900, making his authorial debut as a poet publishing in the magazine Alvoorder. It was, however, as a writer of prose that he achieved much of his fame. Whilst living in Rotterdam he wrote Villa des Roses (1913), his acclaimed novel revolving around the (mis)adventures of the guests of a Paris boardinghouse. His most famous works were written in the 1920s and 1930s: Lijmen (1924), Kaas (1933), Tsjip (1934) en Het Been (1938), novels with both tragic and comedic elements.