Agathonisi is the northernmost island of the Dodecanese complex and is located a short distance south of Samos. According to its geographical position, it is the northeastern border between the Dodecanese and the sea area with the nearby coasts of Asia Minor, mainly the mouths of the Meander River and Miletus. The island has an area of ​​14.4 and coastline 32 km and road network about 10 km. It is 25 nautical miles from Patmos, 18 from Samos and only 8 miles from the coasts of Asia Minor. The permanent population is 186 inhabitants (according to the 2011 census). During the Talocracy, the island was named Gaidouronisi, indicative of its shape, and so it is written on many nautical charts. The current name Agathonisi is due to the paretymology of the Agathochortos plant that grows abundantly on the island. Agathonisi is surrounded by six islets: Kouneli or Kounelonisi in the south, Nero or Neronisi, Stroggili or Stroggylo, Pita or Piato or Psathonisi or Psatho and Praso in the north and Katsagani or Glaro in the east. It is an ideal place for boating.

Agathonisi has two settlements: Megalo Chorio which extends to the port of Agios Georgios. It is the largest and oldest settlement. It was built on a site that is invisible from the sea to protect residents from pirate raids. In recent years the settlement has expanded and is developing to the port of Agios Georgios. The Small Village It is built opposite the Big Village. The port of Agios Georgios has a wide and large pier facing south, protecting small and large boats safely from the north winds. It has small coves and small sandy beaches around it.


In the area of ​​Agios Georgios near the port, a two-aisled church has been built in honor of Agios Georgios and Agios Nektarios. In the small village and at the top of the mountain, Agios Panteleimon. In Megalo Chorio the two-aisled church of Zoodochos Pigi and Agios Ioannis the Theologian and next to Agios Raphael. In the area and beyond Megalo Chorio we find the chapels: Agioi Anargyroi, Agios Ioannis Prodromos, Agia Irini Chrysovalantou and high on the top of the mountain Kefala Agios Charalambos. On the road to Katholiko is the chapel of the Transfiguration of the Savior and in the area of ​​Tholoi of Agios Nikolaos.