William Pitt Richardson (May 25, 1824 – August 4, 1886) was a Republican politician from the state of Ohio, USA. He was Ohio Attorney General in 1865. Richardson was born on May 25, 1824, at Washington County, Pennsylvania. He entered Washington College in 1841, and graduated in 1844. He was then a teacher, and remained so after moving to Ohio. He enlisted as a private in the Third Ohio Infantry in 1846, and served in the Mexican–American War. In 1852, he was elected Prosecuting Attorney of Monroe County, Ohio, and held that office until 1861. During the Civil War, he enlisted as a Major in the 25th Ohio Infantry, was promoted to Lieutenant Colonel and Colonel. On May 2, 1863, at the Battle of Chancellorsville, he was wounded and lost use of his right arm.