The megaron (; Ancient Greek: μέγαρον, [mégaron]), plural megara , was the great hall in very early Mycenean and ancient Greek palace complexes. Architecturally, it was a rectangular hall that was surrounded by four columns, fronted by an open, two-columned portico, and had a central, open hearth that vented though an oculus in the roof.

The megaron also contained the throne-room of the wanax, or Mycenaean ruler, whose throne was located in the main room with the central hearth. Similar architecture is found in the Ancient Near East though the presence of the open portico, generally supported by columns, is particular to the Aegean. Megara are sometimes referred to as "long-rooms", as defined by their rectangular (non-square) shape and the position of their entrances, which are always along the shorter wall so that the depth of the space is larger than the width. There were often many rooms around the central megaron, such as archive rooms, offices, oil-press rooms, workshops, potteries, shrines, corridors, armories, and storerooms for such goods as wine, oil and wheat. Evidence suggests that the megara of ancient Greece were often created using the construction techniques of “Wattle-and-Daub” and “Pisé”.

The megaron is thought to have been used for sacrificial processions, as well as for royal functions and court meetings. However, parts of the megaron functioned as habitable spaces, and were utilized as living quarters prior to the eighth century BC.