Lieutenant Commander Lang was a male Human Starfleet officer in the 23rd century. He served in the command division aboard the USS Enterprise in 2267 under the command of Captain James T. Kirk, during the historic five-year mission. He was one of the ship's gunnery officers.
That same year, Lang was one of three tactical aides who beamed to the Earth observation outpost on Cestus III in 2267. Arriving, they discovered the colony had been destroyed by the Gorn, a previously unknown species. Captain Kirk ordered Lang to look for survivors. Shortly after this, Lang was killed. Of the three aides, only Lieutenant Kelowitz survived this attack. (TOS: "Arena")