Batis (or Bates) of Lampsacus, was a student of Epicurus at Lampsacus in the early 3rd century BC. She was the sister of Metrodorus and wife of Idomeneus. When her son died, Metrodorus wrote to his sister offering comfort, telling her that "all the Good of mortals is mortal," and "that there is a certain pleasure akin to sadness, and that one should give chase thereto at such times as these." Epicurus, for his part, wrote a letter to Batis on the death of Metrodorus in 277 BC.
Among the various fragments of letters discovered among the papyri at Herculaneum, some may have been written by Batis.