William B. Harrison was the flight officer aboard the SS Beagle in the early 2260s.
When the Beagle was damaged and abandoned in 2262, Captain Merick ordered his crew to the surface of planet 892-IV; Harrison was captured, along with the rest of the crew, by the inhabitants of 892-IV and forced to fight as a Roman gladiator after he refused to adapt to the Roman way of life.
Harrison was killed in 2268 by a gladiator named Claudius Marcus. His demise was observed, after the fact, by the crew of the USS Enterprise via black-and-white Empire TV news footage shown on the viewscreen. He was described as "The last of the Barbarians" excluding Captain R.M. Merik who had agreed to become a Roman and live on the planet. (TOS: "Bread and Circuses")