A starship in the Mirror Universe, the Avenger was commanded by Admiral Black.

The Defiant, under the command of the Mirror Universe's Jonathan Archer, came to the Avenger's aid during a rebel attack. The Avenger joined the Defiant at warp, soon after Admiral Black boarded Archer's starship from the future.

After Archer killed Black with a hand phaser from the Defiant, the Avenger's crew joined the Defiant, with the Avenger presumably scuttled.