Thuringwethil is Sindarin for "Woman of secret shadow". She was a messenger of Sauron in J.R.R. Tolkien's The Silmarillion. One of the Maiar, her shape was that of a vampire-bat. She carried messages to and from Tol-in-Gaurhoth and Angband. She was slain by Huan in the First Age. The corpse was taken by Huan and used by Lúthien Tinúviel to reach Beren before he came to Anfauglith and Angband in his quest for a silmaril.