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.
Theodoureas (Qasr Libya) is a minor settlement in northern Libya approximately northwest of Bayda. Historically, it was referred to as Olbia and Theodorias, with archaeological digs conducted during the 1950s.