The Anglo-Saxons, in some contexts simply called Saxons or the English, were a cultural group who spoke Old English and inhabited much of what is now England and south-eastern Scotland in the Early Middle Ages. They traced their origins to Germanic settlers who became one of the most important cultural groups in Britain by the 5th century. The Anglo-Saxon period in Britain is considered to have started by about 450 and ended in 1066, with the Norman Conquest. Although the details of their early settlement and political development are not clear, by the 8th century an Anglo-Saxon cultural identity which was generally called Englisc had developed out of the interaction of these settlers with the existing Romano-British culture. By 1066, most of the people of what is now England spoke Old English, and were considered English. Viking and Norman invasions changed the politics and culture of England significantly, but the overarching Anglo-Saxon identity evolved and remained dominant even after these major changes. Late Anglo-Saxon political structures and language are the direct predecessors of the high medieval Kingdom of England and the Middle English language. Although the modern English language owes less than 26% of its words to Old English, this includes the vast majority of everyday words.

In the early 8th century, the earliest detailed account of Anglo-Saxon origins was given by Bede (d. 735), suggesting that they were long divided into smaller regional kingdoms, each with differing accounts of their continental origins. As a collective term, the compound term Anglo-Saxon, commonly used by modern historians for the period before 1066, first appears in Bede's time, but it was probably not widely used until modern times. Bede was one of the first writers to prefer "Angles" (or English) as the collective term, and this eventually became dominant. Bede, like other authors, also continued to use the collective term "Saxons", especially when referring to the earliest periods of settlement. Roman and British writers of the 3rd to 6th century described those earliest Saxons as North Sea raiders, and mercenaries. Later sources, such as Bede, believed these early raiders came from the region they called "Old Saxony", in what is now northern Germany, which in their own time had become well known as a region resisting the spread of Christianity and Frankish rule. According to this account, the English (Angle) migrants came from a country between those "Old Saxons" and the Jutes.

Anglo-Saxon material culture can be seen in architecture, dress styles, illuminated texts, metalwork and other art. Behind the symbolic nature of these cultural emblems, there are strong elements of tribal and lordship ties. The elite declared themselves kings who developed burhs (fortifications and fortified settlements), and identified their roles and peoples in Biblical terms. Above all, as archaeologist Helena Hamerow has observed, "local and extended kin groups remained...the essential unit of production throughout the Anglo-Saxon period."

In modern times, the term "Anglo-Saxons" is used by scholars to refer collectively to the Old English speaking groups in Britain. As a compound term, it has the advantage of covering the various English-speaking groups on the one hand, and to avoid possible misunderstandings from using the terms "Saxons" or "Angles" (English), both of which terms could be used either as collectives referring to all the Old English speakers, or to specific tribal groups. Although the term "Anglo Saxon" was not used as a common term until modern times, it is not a modern invention because it was also used in some specific contexts already between the 8th and 10th centuries.

Before the 8th century, the most common collective term for the Old-English speakers was "Saxons", which was a word originally associated since the 4th century not with a specific country or nation, but with raiders in North Sea coastal areas of Britain and Gaul. An especially early reference to the Angli is the 6th-century Byzantine historian Procopius, which he apparently heard through Frankish diplomats. He never mentions the Saxons, but he states that a large island called Brittia, which was not far from the Rhine delta. He had heard it was settled by three nations, the Angili, Frissones (Frisians), and Brittones, who were each ruled by their own king. Each nation was so prolific that Brittia sent large numbers of individuals every year to the Franks, who planted them in unpopulated regions of their territory.

By the 8th century the Frisians and Saxons living on the continent (both of whom Procopius never mentions) were seen as two distinct countries, and writers such as Bede and some of his contemporaries including Alcuin, and Saint Boniface, began to refer to the overall group in Britain as the "English" people (Latin Angli, gens Anglorum or Old English Angelcynn). In Bede's work the term "Saxon" is also used to refer sometimes to the Old English language, and also to refer to the early pagan Anglo-Saxons before the arrival of Christian missionaries among the Anglo-Saxons of Kent in 597. The term "Saxon", on the other hand, was at this time increasingly used by mainland writers to designate specific northern neighbours of the Frankish kingdom of Austrasia. Bede therefore called these the "Old Saxons" (antiqui saxones), and he believed that there was no longer any country of Angles in Germany, as it had become empty due to emigration.

Similarly, a non-Anglo-Saxon contemporary of Bede, Paul the Deacon, referred variously to either the English (Angli), or Anglo-Saxons (Latin plural genitives Saxonum Anglorum, or Anglorum Saxonum), which helped him distinguish them from the European Saxons who he also discussed. In England itself this compound term also came to be used in some specific situations, both in Latin and Old English. Alfred the Great, himself a West Saxon, was for example Anglosaxonum Rex in the late 880s, probably indicating that he was literally a king over both English (for example Mercian) and Saxon kingdoms. However, the term "English" continued to be used as a common collective term, and indeed became dominant. The increased use of these new collective terms, "English" or "Anglo-Saxon", represents the strengthening of the idea of a single unifying cultural unity among the Anglo-Saxons themselves, who had previously invested in identities which differentiated various regional groups.

In contrast, Irish and Welsh speakers long continued to refer to Anglo-Saxons as Saxons. The word Saeson is the modern Welsh word for "English people"; the equivalent word in Scottish Gaelic is Sasannach and in the Irish language, Sasanach. Catherine Hills suggests that it is no accident "that the English call themselves by the name sanctified by the Church, as that of a people chosen by God, whereas their enemies use the name originally applied to piratical raiders".