The names of two of Conchobar's houses can be translated as "Red Branch", as Old Irish had two words for "red". The Cróeb Ruad or Craoibh Ruadh ("dull red branch") was where the king sat; its name has survived as the townland of Creeveroe in County Armagh. There is a small debate over whether the name was, in fact, Red Branch or Royal Branch, with at least one historian pointing out that a scribe could have mis-transcribed riadh ("royal") as ruadh. The Cróeb Derg or Craoibh Dearg ("bright red branch") was where the severed heads and other trophies of battle were kept. His third house was called the Téite Brec or "speckled hoard", where the heroes' weapons were stored.
In later stories the Red Branch was taken to be the name of the order of warriors, known as the Red Branch Knights, who fought for and protected Conchobar. Cúchulainn was said to be their greatest warrior. The stories of the Red Branch Knights and the Ulster court at Emain Macha are aristocratic in nature - the warriors being high born and in some cases semi-divine, or nemed in Old Irish. Tales of their combat, particularly in the Táin Bó Cúailnge, describe how the Red Branch warriors were driven to battle in chariots and fought either mounted or dismounted with spears and swords. A major feature of their warfare was the description of single combat, where a champion such as Cúchulainn fought a nominated champion of the opposing army to decide the outcome of a battle.
The stories of the Red Branch Knights, though centred around Emain Macha in Ulster, take place all around Ireland and even further afield. For instance, the hero Cuchulain gets his warrior training from a woman named Scáthach in the Western Isles of Scotland.
The legends of the Red Branch Knights were originally part of a Gaelic bardic or oral tradition. With the coming of Christianity and Literacy to Ireland in around the fifth century AD they were written down by Christian monks. The oldest written account of the stories are in the Book of the Dun Cow, composed in the monastery at Clonmacnoise. Another early account appears in the Book of Leinster. Although written by Christian monks, the essentially pagan character of the myths seem to have been preserved, complete with traditional Irish deities.
The name Red Branch Knights was used by a loyalist paramilitary group from Northern Ireland in September 1992 to claim responsibility for incendiary devices and a blast bomb left in a Dublin- based bank in Newtownabbey. Statements were sent to the media threatening action against anyone with political or economic links with the Republic of Ireland. They are not known to have been responsible for any casualties during the Troubles.
The name "Knights of the Red Branch" was also used by an Irish Catholic fraternal organization in Philadelphia, Pennsylvania in the 19th and early 20th centuries.