William W. Chapman, American lawyer and politician (d. 1892)
William Williams Chapman (August 11, 1808 – October 18, 1892) was an American politician and lawyer in Oregon and Iowa. He was born and raised in Virginia. He served as a United States Attorney in Iowa when it was part of the Michigan and Wisconsin territories, and then represented the Iowa Territory in the United States House of Representatives. He later immigrated to the Oregon Country, where he served in the Oregon Territorial Legislature.

After settling in Portland, he helped to found The Oregonian newspaper and promoted economic interests in the city. He also was involved with building Canyon Road near Portland, and fought in the Rogue River War in Oregon. In later years, he served in the Oregon Legislative Assembly and promoted the expansion of railroads from Portland. Chapman Square, a park in downtown Portland, is named for him and was built on land he sold to the city.