Q was a member of the Q traditionalists in the Q Continuum during the Q Civil War in 2373.
In an illusion of the American Civil War, created by Q so that Kathryn Janeway could comprehend the Continuum, this Q was represented as a private in the Confederate Army, serving under Colonel Q.
Following Q and Janeway's capture, he stood guard outside the Colonel's tent on the morning of their planned execution, where he was saluted by Captain Q upon the latter's arrival to escort the two prisoners to the firing squad. (VOY: "The Q and the Grey")
This private was played by an unknown actor.