The Saxons, sometimes called the Old Saxons or Continental Saxons, were a Germanic people of early medieval "Old" Saxony (Latin: Antiqua Saxonia) which became a Carolingian "stem duchy" in 804, in what is now northern Germany, between the lower Rhine and Elbe rivers. Many of their neighbours were, like them, speakers of West Germanic dialects, including both the Franks and Thuringians to the south, and the coastal Frisians and Angles to the north who were among the peoples who were originally referred to as "Saxons" in the context of early raiding and settlements in Roman Britain and Gaul. To their east were Obotrites and other Slavic-speaking peoples.

The political history of these continental Saxons is unclear until the 8th century and the conflict between their semi-legendary hero Widukind and the Frankish emperor Charlemagne. They do not appear to have been politically united until the generations of conflict leading up to that defeat, before which they were reportedly ruled by regional "satraps". Previous Frankish rulers of Austrasia, both Merovingian and Carolingian, fought numerous campaigns against Saxons, both in the west near the Lippe, Ems and Weser, and further east, near Thuringia and Bohemia, in the area which later medieval sources referred to as "North Swabia". Charlemagne conquered all the Saxons after winning the long Saxon Wars (772–804 AD) and forced them to convert to Christianity, annexing Saxony into the Carolingian domain. Under the Carolingian Franks, Saxony became a single duchy, fitting it within the basic political structure of the later Holy Roman Empire. The early rulers of this Duchy of Saxony expanded their territories—and therefore those of the Holy Roman Empire—to the east, at the expense of Slavic-speaking Wends.

Long before any clear historical mention of Saxony as a state, the name "Saxons" was also used to refer to coastal raiders who attacked the Roman Empire from north of the Rhine, in a similar sense to the much later term Viking. These early raiders and settlers included Frisians, Angles and Jutes, and the term Saxon was not at that time a term for any specific tribe.

Earlier still, there is a single possible classical reference to a smaller and much earlier Saxon tribe in the second century AD, but the interpretation of this text ("Axones" in most surviving manuscripts) is disputed. For historians who accept this record, the original Saxon tribe lived north of the mouth of the Elbe, close to the probable homeland of the Angles, in the part of later Saxony which came to be known later as Nordalbingia.

Today the Saxons of Germany no longer form a distinctive ethnic group or country, but their name lives on in the names of several regions and states of Germany, including Lower Saxony (German: Niedersachsen) which includes most of the original duchy. Their language evolved into Low German which was the lingua franca of the Hanseatic League, but has faced a long and gradual decline since the Late Medieval period as a literary, administrative and, to a significant extent, cultural language in favor of Dutch and German.

The name of the Saxons has traditionally been said to derive from a kind of knife used in this period and called a seax in Old English and sachs in Old High German. The term "Saxon" was first definitely used in written records to describe coastal raiders who attacked the Roman Empire from regions north of the Rhine using boats. At this time, the term had a similar sense to the much later term "Viking". These early raiders and settlers called Saxons included Frisians, Angles and Jutes, whose countries stretched from what is now the Netherlands to what is now Denmark, and included coastal parts of the territory which came to be called Saxony. It has been proposed that these coastal Saxons, who were strongly associated with the Anglo-Saxons of England, should be seen as distinct from the later Saxons of Carolingian times, although they were referred to by the same name, and were clearly related peoples. This has been compared to the later evolution of modern European terms referring to the "Dutch people" of the Netherlands, and the Deutschen, or Germans, of neighbouring Germany.

Significant numbers of these early Saxons settled within the empire, in what later became northern France and England. England, rather than Saxony, was sometimes written of as the Saxon homeland. To avoid confusion, later writers in the 8th century such as Bede and the author of the Ravenna Cosmography referred to the Saxons of Saxony in Germany as the "old Saxons", and their country as "old Saxony", and this differentiation is still often used by historians today when discussing this period. In contrast, the settlers once called Saxons in England became part of a new Old English-speaking nation, now commonly referred to as the Anglo-Saxons, or simply "the English". This brought together local Romano-British populations, Saxons, and other migrants from the same North Sea region, including Frisians, Jutes, and Angles. The Angles are the source of the term "English" which became the more commonly used collective term. The term "Anglo-Saxon", combining the names of the Angles and the Saxons, also came into use by the 8th century, initially in the work of Paul the Deacon, to distinguish the Germanic-speaking inhabitants of Britain from continental Saxons. However, both the Saxons of Britain and those of Old Saxony in northern Germany long continued to be referred to as "Saxons" in an indiscriminate manner.

Ptolemy's Geographia, written in the 2nd century, is sometimes considered to contain the first mention of the Saxons. Some copies of this text mention a tribe called Saxones in the area just to the north of the lower Elbe, and there were also three islands north of the Elbe's mouth which were called the Saxon islands. However, other versions refer to the same tribe as Axones. Some scholars such as Mathias Springer have proposed that this may be a misspelling of the tribe that Tacitus in his Germania called Aviones. According to this theory, Saxones was the result of later scribes trying to correct a name that meant nothing to them. On the other hand, Schütte, in his analysis of such problems in Ptolemy's Maps of Northern Europe, believed that Saxones is correct. He notes that the loss of first letters occurs in numerous places in various copies of Ptolemy's work, and also that the manuscripts without Saxones are generally inferior overall. According to Liccardo "Even though the reference is found in a section of the Geographia difficult to interpret, the scholarly consensus considers this passage to be genuine".