William Horace Warner (8 May 1812 – 26 September 1849) was an officer in the United States Army's Corps of Topographical Engineers. In 1849, he led an Army survey party north from Sacramento through the uncharted country of northeastern California into south central Oregon. Warner was killed by Native Americans in northeastern California, just south of the Oregon border. In the mid-nineteenth century, two army outposts in southern Oregon were named after Warner. Today, the Warner Mountains, Warner Valley, and a number of other landmarks bear his name.