Lewis Thornton Powell, also known as Lewis Payne and Lewis Paine, was an American Confederate soldier who attempted to assassinate William Henry Seward as part of the Lincoln assassination plot. Wounded at the Battle of Gettysburg, he later served in Mosby's Rangers before working with the Confederate Secret Service in Maryland. John Wilkes Booth recruited him into a plot to kidnap Lincoln and turn the president over to the Confederacy, but then decided to assassinate Lincoln, Seward, and Vice President Andrew Johnson instead, and assigned Powell the task to kill Seward.
Co-conspirator David Herold was to guide Powell to Seward's home, then help him escape, but fled before Powell was able to exit the Seward home. He arrived at the boarding house run by Mary Surratt, mother of co-conspirator John Surratt, three days later while the police were there conducting a search, and was arrested. Powell, Mary Surratt, Herold, and George Atzerodt were sentenced to death by a military tribunal, and executed at the Washington Arsenal.