Clann Eanruig (pronounced KLAHN YAHN-reegk) is the Gàidhlig (Scots Gaelic) name for the Scottish clan known as "the Hendersons" in English. The words "Scot," "Scots" (not scotch), "Scottish," and "Scotland" derive from the Latin word "Scotus" meaning a Celtic inhabitant of Hibernia (Ireland) at the time of the Roman occupation of southern Britannia (Great Britain), i.e., an Irishman. The Scots of Dál Riata began migrating from northern Ireland to northern Great Britain in the Third Century AD. They settled among the Picts, another Celtic people who preceded them. The Picts tolerated the newcomers, and even intermarried with them.

In 563 AD, Columcille (Saint Columba), an Irish nobleman turned missionary, established a monastery on the Isle of Iona to bring Christianity to both Picts and Scots. The Scots flourished and soon outnumbered the Picts. Pictish rulers sought to protect their ancient ways from the vibrant new culture from Ireland. Nechtan mac Derile became King of Picts in 706. King Nechtan embraced the Roman Christian Church (which paid homage to the Bishop of Rome and worshiped on Sunday) to block the power of the Celtic Christian Church (the faith of Columcille which remained independent and continued to worship on the Sabbath.) King Nechtan retired to a monastery in 724. In 843, Kenneth mac Alpin united the Picts and Scots in a common kingdom. Gàidhlig soon became the dominate language, and eventually Pictish culture was absorbed into a common Scottish identity.

The ancient Picts and Scots followed the Celtic custom of matrilineality. This meant that sons could not depend on their father's status, but instead had to establish domains of the own. Pictish prince Eanruig Mor mac Righ Nechtan (Big Henry the son of King Nechtan) established a distinguished family line. The descendants of Prince Henry were known collectively as “clann Eanruig” meaning the “family of Henry.” The males of the clan took the surname “mac Eanruig” meaning “son of Henry,” which was later translated into English variously as “Henryson,” “Henderson,” “McHenry,” “McHendry,” “MacKendrick,” and such. The females of the clan took the surname “nic Eanruig” meaning “daughter of Henry.” A woman normally kept her own clan surname after marriage, and she could usually depend on her clan's support in a dispute with her husband. Families could give children the clan surname of either their mother or father. Over time, the descendants of other prominent Henrys also took the family name "clann Eanruig." Eventually, the most prominent of these families coalesced into a single clan identity.

In contrast to the social equality of the Celtic Picts and Scots, the Germanic Angles and Saxons were patriarchal and patrilineal societies. The father ruled the family and all family members took his surname. After England conquered Scotland, the Scots gradually adopted many of these customs.

Though a small clan, the Hendersons rose to prominence in Glencoe, Caithness, the Shetland Islands, Liddlesdale, and Fordell. In Glencoe, Clan Henderson forged a close alliance with the powerful Clan Donald. In 1692, King William III, suspecting the loyalty of Clan Donald, secretly set the Campbells upon the MacDonalds and Hendersons in the Massacre of Glencoe. After the Massacre, many Henderson families emigrated to Ulster and North America.

Hendersons in the British colonies of North America played an important role in the American drive for independence from Britain. Loyalist Hendersons played an important role in the British settlement of Canada. More Henderson familes left Scotland for England, Ireland, North America, Australia, New Zealand, and other lands during the the Highland Clearances. Today, Hendersons encircle the globe.

The modern surnames of the Clan Henderson include d'Handresson, Eanrig, Eanruig, Enderson, Endherson, Endirsone, Enrick, Enrig, Henders, Henderson, Hendersone, Hendersonne, Hendersoun, Hendersoune, Hendery, Hendirsone, Hendirsoune, Hendrie, Hendrisoune, Hendron, Hendry, Henersoun, Hennersoune, Hennryson, Henresoun, Henreysoun, Henriesoun, Henrison, Henrisone, Henrisoun, Henrisoune, Henry, Henryesson, Henryson, Henrysoun, Inrick, Inrig, Kendrick, Kenrick, MacCanrig, MacCanrik, MacEanruig, MacEnrick, MacHendric, MacHendrie, MacHendry, MacHenrie, MacHenrik, MacHenry, MacKanrig, MacKendree, MacKendric, MacKendrich, MacKendrick, MacKendrie, MacKendrig, MacKendry, MacKenrick, Makanry, Makhenry, McHendry, McHenry, McKendree, McKendrick, and McKendry.