Hayk also known as Hayk Nahapet, is the legendary patriarch and founder of the Armenian nation.

His story is told in the History of Armenia attributed to the Armenian historian Moses of Chorene (Movses Khorenatsi) and in the Primary History traditionally attributed to Sebeos. Fragments of the legend of Hayk are also preserved in the works of other authors, as well as in Armenian folk tradition.

The name of the patriarch, Hayk, is not exactly homophonous with the Armenian name for "Armenia," Haykʻ. In Classical Armenian, Haykʻ is the nominative plural of hay, the Armenian word for "Armenian."While Robert W. Thomson considers the etymology of Haykʻ (Հայք) from Hayk (Հայկ) to be impossible,other scholars consider the connection between the two to be obvious and derive Hayk from hay/Haykʻ via the suffix -ik. Armen Petrosyan proposes a possible connection between the name Hayk and the Proto-Indo-European *poti- "master, lord, master of the house, husband." Armenian historiography of the Soviet era connected Hayk and hay with Hayasa, a people mentioned in Hittite inscriptions. Some authors derive Hayk and hay from Khaldi/Ḫaldi, the chief god of the Urartian pantheon, and also identify Hayk with the Urartian deity.The Armenian word հaykakan derives from the name Hayk. Additionally, the poetic names for the Armenian nation, Haykazun or Haykazn, also derive from Hayk (Haykazn/Haykaz later became a masculine given name among Armenians).

Integrating the Armenian tradition into biblical tradition, Moses of Chorene describes Hayk as a descendant of Noah through the latter's son Japheth: "Yapheth begat Gamer; Gamer begat T‘iras; T‘iras begat T‘orgom; T‘orgom begat Hayk." Hayk's descendants through his son Aramaneak (Aramanyak) are listed as follows: "Aramaneak begat Aramayis; Aramayis begat Amasya; Amasya begat Gełam; Gełam begat Harmay; Harmay begat Aram; Aram begat Ara the Handsome.'' Hayk's other sons, according to Moses, were Khoṛ and Manavaz. Moses also gives the names of numerous other descendants of Hayk (Haykazunis, "of Hayk's lineage," also known as the Haykids), such as Sisak, Skayordi, Paruyr, and Vahe, some of which he identifies as kings of Armenia. In reference to Hayk's descent from Torgom/Togarmah, medieval Armenian sources sometimes referred to Armenia as T‘orgoma tun ("House of Torgom") and to Armenians as T‘orgomyan azg ("the people of Torgom"). The connection between Hayk and the descendants of Noah was created by Christian authors following the Christianization of Armenia in order to connect Armenians to the biblical narrative of human history.

In the Georgian history attributed to Juansher, Hayk is likewise identified as the son of Torgom/Togarmah and described as "prince of the seven brothers and stood in service to the giant Nimrod (Nebrovt') who first ruled the entire world as king."

One of Hayk's most famous scions, Aram (whose name Moses purports to be the origin of the name Armenia), settled in Eastern Armenia from the Mitanni kingdom (Western Armenia), when Sargon II mentions a king of part of Armenia who bore the (Armenian-Indo-Iranian) name Bagatadi (which, like the Greek-based "Theodore" and the Hebrew-based "Jonathan," means "god-given").

Hayk was a handsome, friendly man, with curly hair, sparkling eyes, and strong arms. He was a man of giant stature, a mighty archer and fearless warrior. Hayk and his people, from the time of their forefathers Noah and Japheth, had migrated south toward the warmer lands near Babylon. In that land there ruled a wicked giant, Bel. Bel tried to impose his tyranny upon Hayk's people. But proud Hayk refused to submit to Bel. As soon as his son Aramaniak was born, Hayk rose up and led his people northward into the land of Ararad. At the foot of the mountain he built a village and gave it his name, calling Haykashen.