George C. Cottingham was an American policeman from Washington DC. He served as a detective on the force of Washington provost marshal James O'Beirne before interviewing the arrested tavernkeeper John M. Lloyd in the aftermath of Abraham Lincoln's assassination and Mary Surratt's arrest. Surratt's defense attorney Frederick Aiken enlisted Cottingham's help as a defense witness, but Cottingham proved to be a hostile witness and supported Lloyd's testimony.