Qasr Libya or Theodoureas () is a small town in northern Libya about  northwest of Bayda. In ancient times, it was called Olbia and Theodorias, the ruins of which were excavated in the 1950s.
In northern Libya, northwest of Bayda, lies Qasr Libya or Theodoureas (also known as Olbia and Theodorias). Archaeological investigations into its ruins took place during the 1950s.