Carlos Frederick MacDonald, M.D. (August 29, 1845 – May 29, 1926) was a psychiatrist, and the chairman of the New York State Commission in Lunacy from 1880 to 1896. He was involved in the design of the first electric chair and examined Leon F. Czolgosz, pronouncing him sane enough to be executed in the electric chair after the assassination of President William McKinley in 1901. He was President of the American Psychiatric Association from 1913 to 1914. He was an expert witness at the trials of Harry Thaw and Harrison W. Noel.