William Harrison Folsom (March 25, 1815 – March 19, 1901) was an architect and contractor. He constructed many of the historic buildings in Utah, particularly in Salt Lake City. Folsom is probably best known as a Latter-day Saint ("Mormon") architect. Many of his most prominent works were commissioned by the Church of Jesus Christ of Latter-day Saints (LDS Church). For a time he was sustained as the Church Architect, a calling in the church.