Basileia (an Ancient Greek word meaning royal palace) may refer to:
- One of the daughters of Uranus, also called Theia "Delphi Complete Works of Diodorus Siculus"
- The royal palace, or citadel, of Atlantis, as described by the Greek philosopher Plato in the Critias
- The royal quarter of Ptolemaic Alexandria
- The Kingdom of God (basileia tou theou), or Kingdom of Heaven, in Christian theology
- Basileia, Zeus's maid in the play The Birds by Aristophanes
- Basileia Romaion, the Greek name for the Eastern Roman Empire, translated as Roman Empire or 'Empire of the Romans'
- Basileia Theological Journal, a theological journal published biannually by Central India Theological Seminary.
- A feminine form for Basileus
- An alternative spelling of Basel, Switzerland's third-most-populous city