Anonymus Londinensis (or Anonymus Londiniensis) is the name given to an anonymous Ancient Greek author of approximately the 1st century AD, whose work On Medicine (Ancient Greek: Ἰατρικά, Latin: De Medicina) is partially preserved in a papyrus in the British Library (PBrLibr inv. 137 = P.Lit.Lond. 165). The paprus was found in Egypt. It ranks as the most important surviving medical papyrus and provides important information about the history of Greek medical thought.