William Marcy Whidden (February 10, 1857 – July 27, 1929) was a founding member of Whidden & Lewis, a prominent architectural firm in Portland, Oregon, United States.
In 1889, Ion Lewis and Whidden formed a professional architectural firm in Portland. Their residential buildings were mostly in the Colonial Revival style, while their commercial buildings were primarily in the twentieth-century classical style. The commercial buildings often featured brick, along with terra cotta ornamentation. Many of their buildings are listed on the National Register of Historic Places (NRHP).
The Whidden–Kerr House and Garden, which was William Whidden's residence from 1901 until 1911, is also listed on the National Register.