From around 480 AD Saxons from the south and Jutes from east invaded and began settling in the area and establishing a sub-kingdom probably with Middle Saxon overlords. The name Surrey is Saxon, and is a corrupted form (with r replacing the sound đ) of "Suuđ-ye" meaning "South Ridge" or more probably "south administrative unit" (the Old Germanic district "Gau" like those were established by Charlemagne; earlier German spellings were Gowe, Gouwe), referring to its position on the South bank of the Thames. At this time the Surrey area was sparsely populated and almost entirely forested. There was a local truce recorded in c.500 (possibly as a result of the Battle of Badon Hill) and only north and east Surrey were retained by the Anglo-Saxons. The westward expansion into British territory continued from c.550AD with some local British communities becoming marooned within the confines of Saxon Surrey, probably around Walton-on-Thames. From 568 the eastern border of Surrey and Kent is agreed and marked by a ditch. Local tribes named Æschingas, Godhelmingas (around Godalming), Tetingas (around Tooting), Woccingas (between Woking and Wokingham), Basingas (the Blackwater Valley) and Sonningas (around Sonning) are known to have existed.

In 661 the sub-kingdom took Mercia as its overlord. In 675 Surrey became one of the last portions of England to convert to Christianity when its sub-King Frithuwold and his son were baptised. The name of the area at this time is recorded as Sudergeona or "southern region". In 685 Surrey changed allegiance and took Wessex as its overlord. In 690 the western border of Surrey was settled with Wessex; the tribal territories of the Sonningas became part of Berkshire and the Basingas became part of Hampshire. In 705 Surrey was transferred from the Middle Saxon diocese of London to the West Saxon diocese of Winchester. After 771 Surrey came under the rule of Offa of Mercia and was so until 823 when Surrey reverted to Wessex and so remained. Some historians have also speculated that the Nox gaga and the Oht gaga tribes listed in the Mercian Tribal Hidage refers to two distinct groups living in Surrey. They were valued together at 7,000 hides.

The West Saxon shire

The territory of Surrey was formally annexed by Wessex in 860 and became a Shire under the same model as the other counties of Wessex. It is around this time that the wars between the Ænglecynn and the Danes reach their height with Surrey becoming the arena for a number of key battles; most notably at the Battle of Ockley in 851 and the Battle of Farnham in 894.

After the death of King Alfred the Great in 899 his son, King Eadweard I was crowned on the King's Stone at Kingston upon Thames. The use of this stone before 902 is unknown but it seems likely that it would have been something of ancient spiritual or political significance. After him another six kings of England from the House of Wessex were crowned here, the last being Æþelræd II in 978.In 1011 it is recorded that Surrey was over-run by Danish forces led by Canute the Great before all of England submitted to them in 1016.

In 1035, Canute died and during the uncertainty that followed the heirs of former Anglo-Saxon rulers attempted to restore the House of Wessex to the throne of Ænglalond. Ælfred Æþling the younger of the two heirs (his older brother being the future Eadweard III) landed on the coast of Sussex with a Norman mercenary body guard and attempted to make his way to London. In the Anglo-Saxon Chronicle there is an account of this fateful encounter:

"As Ælfred and his men approached the town of Guildford in Surrey, thirty miles south-west of London, they were met by the powerful Earl Godwin of Wessex, who professed loyalty to the young prince and procured lodgings for him and his men in the town. The next morning, Godwin said to Ælfred: "I will safely and securely conduct you to London, where the great men of the kingdom are awaiting your coming, that they may raise you to the throne." This he said in spite of the fact that the throne was already occupied by the son of Knud, Harold Harefoot, and he was actually in league with King Harold to lure the young prince to his death."

"Then the earl led the prince and his men over the hill of Guildown (called today The Hog's Back and is the route of the A31), which is to the west of Guildford, on the road to Winchester, not London. Perhaps the prince had insisted on continuing his journey to his original destination, his mother’s court in Winchester, in any case, Godwin repeated his tempting offer; showing the prince the magnificent panorama from the hill both to the north and to the south, he said: "Look around on the right hand and on the left, and behold what a realm will be subject to your dominion." Ælfred then gave thanks to God and promised that if he should ever be crowned king, he would institute such laws as would be pleasing and acceptable to God and men. At that moment, however, he was seized and bound together with all his men. Nine tenths of them were then murdered. And since the remaining tenth was still so numerous, they, too, were decimated."

Interestingly, during the 1920s the remains of several hundred soldiers, probably Normans, were found to the west of Guildford. They were bound and had been executed. The grave was dated to c.1040. It is likely that they were the guards of poor Prince Ælfred.

After the Anglo-Saxon restoration through the accession of Eadweard III in 1042 Surrey remained unmolested until the Norman Conquest in 1066.

Few remains of the ancient British, the Roman, or the Saxon periods in Surrey exist. There is an Iron Age hillfort at Holmbury Hill, and only remnants of the Roman roads Stane Street and Ermine Street remain. Roman and celtic relics, of no great significance, have been found at various locations.