Gihon is the name of a river first mentioned in the second chapter of the Biblical book of Genesis. The Gihon is mentioned as one of four rivers (along with the Tigris, Euphrates, and Pishon) issuing out of the Garden of Eden that branched from a single river within the garden. The name (Hebrew Giħôn) may be interpreted as "Bursting Forth, Gushing".
The Gihon is described as "encircling the entire land of Cush", a name associated with Ethiopia elsewhere in the Bible. This is one of the reasons that Ethiopians have long identified the Gihon with the Abay River, which encircles the former kingdom of Gojjam. From a current geographic standpoint this would seem impossible, since two of the other rivers said to issue out of Eden, the Tigris and the Euphrates, are in Mesopotamia. However, the scholar Edward Ullendorff has argued in support of this identification. The city in the Mesopotamian area which best fits the description is called Kish (derivative of Kush or Cush) located in a plain area (Sumerian 'edin') and resembles an area that is repeatedly flooded by the rivers today called Euphrates and Tigris.
Nineteenth century, Modern, and Arabic scholars have sought to identify the "land of Cush" with Hindu Kush, and Gihon with Amu Darya (Jihon/Jayhon of the Islamic texts). Amu Darya was known in the medieval Islamic writers as Jayhun. This was a derivative of Jihon, or Zhihon as it is still known by the Persians.
Gihon has also been associated with the Araxes (modern Aras) river of Turkey. Another proposed idea is that the Gihon river no longer exists, or has significantly altered its course, since the topography of the area has supposedly been altered by the Noachian Flood.
Some modern secular scholars note that the Gihon river remains unidentified, since the geographical ideas of the author(s) of Genesis cannot be reconstructed and need not conform with actual geography as known today: In Genesis 2, the Euphrates, Tigris, Gihon and Pishon rivers are all said to issue out of Eden and become 'four heads', but the Euphrates and the Tigris do not take their rise in the same place, and the Pishon river remains as unidentified.
First-century Jewish historian Josephus associated the Gihon river with the Nile (Jewish Antiquities, 1.39). However, a quite different Hebrew word is used to designate the Nile elsewhere in the Bible, and even in ancient times it should have been obvious that the Nile could not have a common source with the Tigris and the Euphrates.
Gihon is also the name of the only natural spring of water in the vicinity of Jerusalem. It feeds the Pool of Siloam. See "Gihon Spring". The Book of Jasher refers to the "Great Sea Gihon", which is believed to mean the Atlantic Ocean.