George Duncan Hastie McMillan, Jr. (born October 11, 1943) is an American Democratic politician who served as the 23rd lieutenant governor of Alabama from 1979 to 1983.

In 1989 he founded the City Stages music festival in downtown Birmingham, Alabama.

McMillan was elected to the Alabama House of Representatives and served for one term in 1973.

McMillan ran in the Democratic gubernatorial primary election in 1982, but was beaten by former Governor George Wallace, coming in second place.

A run-off election was held between McMillan and Wallace, which Wallace won, going on to win the general election against Republican Mayor Emory Folmar of Montgomery.