Delium, town of ancient Greece, a port in E Boeotia, named for its temple of Apollo similar to the one at Delos. In the Peloponnesian War the Athenians were defeated (424 B.C.) by the Boeotians there; Socrates fought in the battle.

Delium (also called Delion Greek: Δήλιον Dêlion, Latin: Delium) was a Greek city famous for its important temple dedicated to Apollo, similar to the one in Delos, thence its name. Founded by colonists of Tanagra, it was located approximately 2 km from Oropos and 8 km from Tanagra.

There were two important battles in Delium:

• In the first battle, called the Battle of Delium, the Athenians were defeated by the Boeotians in 424 BC. This was part of the Peloponnesian War.
• In a second battle, the Romans were defeated by Antiochus III the Great in 192.