Agathonisi (Greek Αγαθονήσι) is a small island and community (Κοινότητα Αγαθονησίου) located at the northernmost point of the Dodecanese prefecture in Greece. It is surrounded by many smaller islands and is home to two villages; Megalo Chorio, and Mikro Chorio. The Port of Agathonisi is located on Saint George (Agios Georgios) and is the place that you can find the few hotels of Agathonisi.
Agathonisi is another small island which belongs to the Province of Kalymnos and is situated east of Patmos, about 2 hours and 30 minutes by boat. The island goes by other names such as the locally preferred name of Gaidaros and the ancient name Tragea.
The highest point on the island is 209 metres above sea level. This peak is located close to Mikro Chorio. The island covers an area of 13.5 km².
A census of the island in 1981 showed that it was populated by 133 people. In 1991, another census showed that the population had dropped to 112. By the 2001 census it had again risen to 158 residents, 144 of whom lived in Megalo Chorio, and only 14 in Mikro Chorio. The Community of Agathonisi, which includes the uninhabited offshore islets of Glaros, Kouneli, Nera, and Psathonisio, has a combined land area of 14.500 km². Of this population few speak English, one or two speak German or Italian.