William Henson Wallace (born July 19, 1811 in Troy, Ohio – died February 7, 1879 in Steilacoom, Washington) was the first governor and Congressional delegate from Idaho Territory, and was the younger brother, by 12 years, of David Wallace who was a governor of Indiana. Wallace also represented Washington Territory as a Congressional delegate.

After being admitted to the bar, he moved to Iowa in 1837, William was a member of Iowa territorial House of Representatives, 1838; member Iowa territorial council, 1842-43; candidate for Delegate to U.S. Congress from Iowa Territory, 1843; candidate for U.S. Senator from Iowa, 1848; moved to the Territory of Washington in 1853; member of the Territorial council in 1855 and 1856 and served as president of the council; appointed Governor of the Territory of Washington in 1861, but did not qualify, having been elected as a Republican a Delegate from the Territory of Washington to the Thirty-seventh Congress (March 4, 1861-March 3, 1863).

As the Congressional delegate from Washington Territory in 1861, he served a single term. In 1863, President Abraham Lincoln appointed him governor of the newly-formed Idaho Territory. Wallace served as governor until he was elected the Congressional delegate from Idaho Territory in 1864 and served from February 1, 1864, to March 3, 186 .

In April 1865, Wallace and his wife were among several people who turned down an invitation from Lincoln to accompany him to Ford's Theatre on the night Lincoln was assassinated.