An ermine violin was a hypothetical musical instrument mentioned by Spock in a conversation in 2268.

That year, when countering Spock's criticism that tribbles seemed to have no practical use, Leonard McCoy seemed to feel it was enough that the creatures were "nice, soft, furry and they make a pleasant sound." Spock objected, saying the doctor's statements would also apply to an ermine violin, but he saw no value in having one of those either. (TOS: "The Trouble with Tribbles")