The Thebaid or Thebais (Greek: Θηβαΐδα, Thēbaïda or Θηβαΐς, Thēbaïs) is the region of ancient Egypt containing the thirteen southernmost nomes of Upper Egypt, from Abydos to Aswan. It acquired its name from its proximity to the ancient Egyptian capital of Thebes.
In Ptolemaic Egypt, the Thebaid formed a single administrative district under the Epistrategos of Thebes, who was also responsible for overseeing navigation in the Red Sea and the Indian Ocean.
During the Roman Empire, Diocletian created the province of Thebais, guarded by the legions I Maximiana Thebanorum and II Flavia Constantia. This was later divided in Upper (Latin: Thebais Superior, Greek: Ἄνω Θηβαΐς, Anō Thēbaïs), comprising the southern half with its capital at Thebes, and Lower or Nearer (Latin: Thebais Inferior, Greek: Θηβαΐς Ἐγγίστη, Thēbaïs Engistē), comprising the northern half with capital at Ptolemais.
Around the 5th century, since it was a desert, the Thebaid became a place of retreat of a number of Christian hermits, and was the birthplace of Pachomius. In Christian art, the Thebaid was represented as a place with numerous monks.