|Regional unit:||East Attica|
|Municipal unit:||Kalyvia Thorikou|
|Time zone:||EET/EEST (UTC+2/3)|
|Elevation (center):||5 m (16 ft)|
|Postal code:||190 10|
Lagonisi (Greek: Λαγονήσι meaning "rabbit island") is a seaside residential area in the southern part of Kalyvia Thorikou in East Attica, Greece. It is situated close to the shore and on a peninsula by the Saronic Gulf. Lagonisi is located approximately 30 km southeast of Athens and 35 km northwest of Cape Sounio. Being filled with luxury homes, beaches as well as prestigious hotels that lie within the Saronic, it is one of the most expensive areas in Attica Prefecture. Restauration facilities, cafeterias and bars are located mainly on the heart of Lagonisi, close to Kalyvion Avenue (the road connecting Lagonisi with Kalyvia Thorikou).
Lagonisi has many beautiful sandy beaches including those of Pefko and Agios Nikolas which are organised. In recent years, the Greek government-debt crisis has led to the privatisation of many state owned properties, including beaches. The state is oriented towards their privatisation, although the locals' opposition makes beaches' future property status uncertain.
The Greek National Road 91 connects Lagonisi with Athens and Sounio. OASA (Athens Urban Transport Organisation) operates a frequent all-year round bus service to and from Elliniko metro station with the designation 122. The average travel time between Lagonisi and Elliniko metro station is about 55 minutes. Furthermore, an inter-municipality bus service operating two to three times per day connects Lagonisi with Kalyvia Thorikou. Taxi service is available as well.