Omonoia Square, Central square in Athens, Greece

Omonoia Square is a central plaza in Athens where six main streets intersect in a circular design, anchored by a modern fountain at its heart. The space is defined by contemporary architectural elements that link the center to the surrounding streets and neighborhoods.

Laid out in 1846 on plans by Stamatios Kleanthis and Eduard Schaubert, the square was first called Plateia Anaktoron (Palace Square) because the royal palace was meant to stand there; the palace went instead to the site of Syntagma. It was renamed Othonos Square for King Otto, and after his deposition in 1862 it took the name Omonoia, "Concord", where rival political leaders swore an oath of peace. The underground Piraeus–Athens railway reached it in 1895, and a station opened beneath it in 1930.

The name Omonoia means "concord": in 1862 the leaders of rival political factions swore an oath of peace here after King Otto was dethroned. The square is also a sports celebration site; after Greece won EuroBasket 2005 and Euro 2004, crowds gathered here, and in 2004 people climbed the Five-ring sculpture with national flags.

The Omonoia metro station below the square connects multiple subway lines and bus routes, making it a major transportation hub for getting around Athens. This makes the square easy to reach from different parts of the city for visitors exploring the area.

A 2020 renovation brought a modern fountain with water jets and LED lighting that creates patterns visible from the surrounding buildings and streets. These lighting elements give the square a contemporary appearance, especially as darkness falls in the evening.