Logres is the name of King Arthur

King Arthur

King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to Medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century. The details of Arthur's story are mainly composed of folklore and literary invention, and...

's realm in the Matter of Britain

Matter of Britain

The Matter of Britain is a name given collectively to the body of literature and legendary material associated with Great Britain and its legendary kings, particularly King Arthur...

. It derives from the Welsh

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

 word Lloegr, a name of uncertain origin meaning "England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

".

In Arthurian contexts, "Logres" is often used to describe the Brittonic territory roughly corresponding to the borders of England before the area was taken by the Anglo-Saxons

Anglo-Saxons

Anglo-Saxon is a term used by historians to designate the Germanic tribes who invaded and settled the south and east of Great Britain beginning in the early 5th century AD, and the period from their creation of the English nation to the Norman conquest. The Anglo-Saxon Era denotes the period of...

. According to Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

's influential pseudohistory Historia Regum Britanniae

Historia Regum Britanniae

The Historia Regum Britanniae is a pseudohistorical account of British history, written c. 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons in a chronological narrative spanning a time of two thousand years, beginning with the Trojans founding the British nation...

, the realm was named after the legendary king Locrinus

Locrinus

Locrinus was a legendary king of the Britons, as recounted by Geoffrey of Monmouth. He was the oldest son of Brutus and a descendant of the Trojans through Aeneas. Following Brutus's death, Britain was divided amongst the three sons, with Locrinus receiving the portion roughly equivalent to...

, the oldest son of Brutus of Troy

Brutus of Troy

Brutus or Brute of Troy is a legendary descendant of the Trojan hero Æneas, known in mediæval British legend as the eponymous founder and first king of Britain...

. In his Historia, Geoffrey uses the word "Loegria" to describe a province containing most of England excluding Cornwall

Cornwall

Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...

, as in this example from section iv.20 (from the Penguin Classics translation by Lewis Thorpe

Lewis Thorpe

Lewis Thorpe B.A. L.-ès-L. Ph.D D. de l'U FIAL FRSA FRHistS was a British philologist, translator, and husband of the Italian scholar and lexicographer Barbara Reynolds. He died on 10 October 1977....

):
The name "Logres" is used in many works of modern fantasy set in Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

, for example C. S. Lewis

C. S. Lewis

Clive Staples Lewis , commonly referred to as C. S. Lewis and known to his friends and family as "Jack", was a novelist, academic, medievalist, literary critic, essayist, lay theologian and Christian apologist from Belfast, Ireland...

's That Hideous Strength

That Hideous Strength

That Hideous Strength is a 1945 novel by C. S. Lewis, the final book in Lewis's theological science fiction Space Trilogy. The events of this novel follow those of Out of the Silent Planet and Perelandra and once again feature the philologist Elwin Ransom...

.