Corporal Adrian Shephard is the player character in Opposing Force, the first expansion pack for the famous first-person shooter computer game Half-Life.

Shephard, a 22-year old United States Marine from the fictional Santego Military Base in Arizona, is one of the special forces sent in the Black Mesa Research Facility to kill the aliens and later silence the witnesses, especially a scientist named Gordon Freeman, the player character in the original game. But everything goes wrong as Adrian finds himself separated from his unit and tries to fight for his life.

Unlike the other soldiers, he works with the increasingly distrustful scientists and guards in order to make it out of Black Mesa alive. Shephard and Freeman do cross paths during the game, but at such points Shephard is merely an observer to some of the climactic events from the original game. He never fights alongside nor against Gordon Freeman. The G-Man character appears to take an interest in Shephard's movements, as early as one week prior to the corporal's involvement in the Black Mesa incident. Shephard deactivates the thermonuclear warhead brought in by the Black Ops, but the G-Man apparently reactivates it and Black Mesa is destroyed. In the end, the G-Man reveals that he has successfully argued for Shephard's life, detaining him in some unknown void.