John Dacher McWilliams (July 23, 1891 – March 30, 1975) was a U.S. Representative from Connecticut. He was born in Norwich, Connecticut to Elizabeth A. (née McClure) and John McWilliams. His father was an immigrant from Ireland. McWilliams attended the public schools and Norwich Free Academy, and graduated from Mercersburg Academy in Pennsylvania in 1910. He worked in the building industry in Norwich, Connecticut. During the First World War, he served as a private in the Twentieth Engineers, United States Army, with overseas service, from March 26, 1918, until discharged on July 1, 1919. He resumed the building business. He served as a selectman of the town of Norwich, Connecticut from 1935 to 1942.