Gareth
Le Morte d'Arthur character
"Sir Gareth of Orkney", Howard Pyle's illustration for The Story of Sir Launcelot and His Companions (1907)
Created by	Thomas Malory
Based on	Gaheriet and Guerrehet
In-universe information
Title	Prince, Sir
Occupation	Knight of the Round Table
Family	Lot, Morgause (parents) Agravain, Gaheris, Gawain, Mordred (brothers) Mordred (half-brother) King Arthur (uncle)
Spouse	Lyonesse
Relatives	King Arthur's family
Home	Orkney, Camelot

Gareth of Orkney (Welsh: [ˈɡarɛθ]) is a Knight of the Round Table in the Le Morte d'Arthur version of the Arthurian legend and many modern works based on it. He is depicted as the youngest son of King Lot and the Queen of Orkney, King Arthur's half-sister, thus making him Arthur's nephew, as well as the youngest brother to Gawain, Agravain and Gaheris.

The author Thomas Malory created (and named) his composite character of Gareth by combining elements of similar figures from French sources (appearing under various names, but originally having been known as Chrétien's Gaheriet and Guerrehet), specifically constructing him as the 'good' Orkney brother. He thus contrasted the virtuous and honourable Gareth with his morally imperfect or even villainous siblings. These includes Malory's Gaheris, whose figure is often being conflated with the Gareth-like youngest of the Orkneys (besides their half-brother Mordred, if he does appear) by other medieval authors, including some texts having the two as one and the same character.

In Le Morte d'Arthur, one of its eight volumes is named after and largely dedicated to a young Gareth, where he is also known by his nickname Beaumains. The story tells, Fair Unknown-style, of his quest on the behalf of the sisters Lynette and Lyonesse, ending in his marriage with the latter and earning his knighthood through both his martial prowess and humility. At the end of Le Morte, Gareth is accidentally killed by his mentor and friend, Lancelot, during the rescue of Guinevere from the stake, an event that leads to the doom of Arthur's kingdom.