Dennis McCarthy was a Starfleet officer in the 24th century.
In 2328, McCarthy was a commercial transport passenger aboard the SS Wisconsin ferried him from Midos V Satellite City Spaceport to Murasaki 312. His passenger manifest was accessed by Lieutenant Commander Data aboard the USS Enterprise-D in 2370 by reviewing this data in the commercial transport database. (TNG: "Inheritance", okudagram)
In 2365, Captain McCarthy was listed as the commander of the USS Apollo on the Starship Deploy Status chart in the Starbase 173 courtroom. (TNG: "The Measure Of A Man", okudagram)
This character was only mentioned in writing.