William Penn Adair (1830–1880) was a leader of the Cherokee Nation. He was born in the traditional Cherokee territory in Georgia. As a child with his family he survived the forced march on the Trail of Tears of Indian Removal from the Southeast to Indian Territory to what is now Oklahoma. He became an attorney who served in public office both before and after the American Civil War and as a justice of their nation's court. He entered the Confederate States Army, and he achieved the rank of colonel. Like many others, he joined on the promise that the Confederacy would support a Native American state if it won the War. He served as Cherokee Nation delegate at Washington, D.C. during the 1860s and 1870s.