William Sargent Ladd (October 10, 1826 – January 6, 1893) was an American politician and businessman in Oregon. He twice served as Portland, Oregon's mayor in the 1850s. A native of Vermont, he was a prominent figure in the early development of Portland, and co-founded the first bank in the state in 1859. Ladd also built the first brick building in Portland and was a noted philanthropist. Part of his former estate, the Ladd Carriage House, is on the National Register of Historic Places.