Winlock W. Steiwer (August 7, 1852 – July 18, 1920) was an American banker, rancher, and politician in the state of Oregon. Born in the Willamette Valley, he made his name in Eastern Oregon as the founder of a bank and as county judge. A Republican, he twice served in the Oregon State Senate. He pleaded guilty in the Oregon land fraud scandal of the early 1900s.