A bouleuterion (Greek: βουλευτήριον, bouleutērion), also translated as council house, assembly house, and senate house, was a building in ancient Greece which housed the council of citizens (βουλή, boulē) of a democratic city state. These representatives assembled at the bouleuterion to confer and decide about public affairs. There are several extant bouleuteria around Greece and its former colonies. It should not be confused with the Prytaneion, which housed the executive council of the assembly and often served as the boule's mess hall.

Athens

The Athenian Boule is better known as the Council of 500. Solon was credited with its formation in 594 BC as an assembly of 100 men each from Athens's four original tribes. At the adoption of the new constitution around 507 BC, this was changed to 50 men each from the 10 newly created tribes. Each served a one-year term.

The Old Bouleuterion was built on the west side of the Agora below the Agoraios Kolonos around 500 BC. It was almost square and included an oblong antechamber and a main council chamber, a large rectangular room with wooden benches arranged in rows along the walls. The roof was supported by five columns. It is now better known as the Metroon ("House of the Mother") since it was repurposed as her temple after the construction of the New Bouleuterion.

The New Bouleuterion was built west of the old building in the late 5th century BC. It was smaller but more sophisticated, with an amphitheater-like system of twelve levels of semicircular benches. Both the Old and the New Bouleuterion used the nearby Tholos.

Olympia

The Bouleuterion of Ancient Olympia was shaped like an early Greek temple, a kind of square horse-shoe. It had a tiered seating arrangement and was located near the city's agora.