John Murphy McMillan Jr. (born July 6, 1941) is an American politician who served as the 40th Treasurer of Alabama. He was elected as a Republican in November 2010 to the office of Alabama Commissioner of Agriculture and Industries. He was elected to a second four-year term in 2014. In 2018, McMillan won the Republican primary election for State Treasurer, and had no Democratic opposition on the general election ballot.