Lieutenant Lewis was a male Human Starfleet officer in the 23rd century. He served aboard the USS Enterprise between 2266 and 2268 under the command of Captain James T. Kirk, during the historic five-year mission. He was one of the ship's security officers.
In 2267, he was part of Lieutenant Commander Giotto's team on Janus VI, hunting for the mother Horta. When Giotto broke his team down, he assigned Lewis and Vinci as two of the team leaders. (TOS: "The Devil in the Dark")
That same year, he and Captain Kirk exited the turbolift onto the bridge of the Enterprise as the search for a cordrazine-injected Leonard McCoy progressed aboard the ship. (TOS: "The City on the Edge of Forever")
Lewis was played by an unknown actor. He also appeared as a Starbase 11 bar patron in "Court Martial", although he was wearing lieutenant commander stripes, so it's unknown if he was indeed the same individual.
Lewis also wore a blue sciences division uniform in "Balance of Terror" and wore a gold command division uniform in "The City on The Edge of Forever". His character was identified by name in "Devil in the Dark".