Fournoi Korseon (), more commonly simplified as Fournoi (), anciently known as Corsiae or Korsiai (), Corseae or Korseai (ÃÂÿÃÂÃÂõñï), Corsia or Korsia (ÃÂÿÃÂÃÂïñ), and Corassiae (ÃÂÿÃÂñÃÂÃÂïñù), form a complex or archipelago of small Greek islands that lie between Ikaria, Samos and Patmos in Ikaria regional unit, North Aegean region. The two largest islands of the complex, the main isle of Fournoi and the isle of Thymaina , are inhabited, as is Agios Minas Island to the east. The municipality has an area of 45.247 km<sup>2</sup>. On the main isle Fournoi (town) is the largest settlement and then Chrysomilia in the north the second largest (and third largest overall, after Thymaina). Fournoi (town) proper is the main ferry harbour, with ferries also landing on Thymaina.
Many of the inhabitants are fishermen, although during the summer season the population is also occupied in tourist activities, mostly room rentals and catering. On the main island are a number of beaches such as Vlychada, Vitsilia, Petrokopio, Elidaki, and Bali.
The archipelago is famous for being a hub of the Ancient World, which resulted in 53 shipwrecks found in the area until 2017. Another five shipwrecks were found in 2018, raising the total number to 58. Those wrecks date back from 4th century BC to 19th century AD.
The climate is arid and hot in the summer. Winters are rather mild with average rainfall but constant strong archipelagic winds prevail.
Transportation is often interrupted during the winter period (mostly from November to April) due to bad weather, mainly strong winds. The rest of the year regular links with the islands of Ikaria and Samos (by boat only) is available. Since 2008 a ferry coming from Samos reaches Athens stopping also in Icaria and Paros.
A shallow-water ship graveyard containing nearly 60 ships lies off Fournoi. Although the site had been plundered and damaged, amphorae as well as a shipment of 2nd-century CE Corinthian terracotta lamps were recovered from some of the ships.
The main island of Fournoi has a population of 1,149 (), 86 percent of the municipality's population. The only other inhabited islands are Agios Minas and Thymaina.