Marousi or Maroussi (Greek: Μαρούσι, also Αμαρούσιο Amarousio) is a suburb in the northeastern part of the Athens agglomeration, Greece. Marousi dates back to the era of the ancient Athenian Republic; its ancient name was Athmonon (Ἄθμονον) and it represented one of the 10 Athenian sub-cities.
The area held a main ancient temple, where Amarysia Artemis, the goddess of hunting, was adored, and the city's modern name derives from that of the goddess, Amarysia, which denotes the origin of the worship back in Amarynthos, Euboea.
Marousi is situated 13 km (8 mi) northeast of Athens city centre. The municipality has an area of 12.938 km2. The built-up area of Marousi is continuous with those of the neighbouring suburbs Pefki, Kifisia, Vrilissia and Halandri. Within Marousi lies the biggest forest in urban Athens, "Dasos Syngrou" (also "Alsos Syggrou"). The Athens Olympic Sports Complex, the largest sports complex in Greece, built for the 2004 Summer Olympics, is located in the southwestern part of the municipality.
The main thoroughfare is Kifisias Avenue, which connects Marousi with central Athens and the northern beltway Motorway 6. Marousi has 3 stations on Athens Metro Line 1 Neratziotissa, Irini and Marousi stations and two suburban (Proastiakos) commuter railway stations: Nerantziotissa station and Kifisias railway station.
Marousi is also home to a number of prestigious public (Peiramatiko Lyceum Anavryton) and private educational institutions.