Who played the Romulan commander in 'Balance of Terror'?

Mark Lenard played the Romulan commander in “Balance of Terror.” The character is never given a personal name in the episode, so the actor’s name is the canonical answer to this casting question.

The episode follows a tense, submarine-style pursuit between the USS Enterprise and a Romulan vessel attacking Federation outposts near the Neutral Zone. Lenard’s commander is a disciplined and intelligent opponent for Captain Kirk, and the two recognize a mutual respect despite fighting on opposite sides. The Romulan ship’s cloaking device and powerful plasma weapon make the encounter especially dangerous.

Viewers sometimes remember Lenard primarily as Sarek, Spock’s Vulcan father, because he returned repeatedly in that role. He also played a Klingon captain in Star Trek: The Motion Picture, giving him the unusual distinction of portraying a Romulan, Vulcan, and Klingon in the franchise. Paul Fix played Dr. Mark Piper, not the Romulan commander.