gnac is a pseudonym used by songwriter and music producer Mark Tranmer. The name is derived from a short story by Italo Calvino in Marcovaldo entitled Luna e GNAC (or "moon and gnac").

Tranmer's music has been described as "imaginary film soundtracks" with comparisons made to Michael Nyman, Ennio Morricone, and Michel Legrand. Vini Reilly has been identified as an influence.