John J. McMahan was South Carolina's seventh State Superintendent of Education from 1898 to 1902. Just shy of thirty years of age after assuming office, he was one of the youngest state superintendents in the state's history.

McMahan attained his A.B. degree from the South Carolina College in 1886. He also attended law school for one year at South Carolina College and subsequently practiced law for the law firm, Lyles and McMahan, from 1903 to 1908. McMahan served in the State Legislature from 1909 to 1910 and from 1915 to 1916. From 1921 to 1928, he was the State Insurance Commissioner. Throughout his career, McMahan wrote and edited a number of books and other publications and worked as associate editor and editor-in-chief for several years.

McMahan died in January 1936.