The Istvaeones (also spelled Istævones) were a Germanic group of tribes living near the banks of the Rhine during the Roman empire which reportedly shared a common culture and origin. The Istaevones were contrasted to neighbouring groups, the Ingaevones on the North Sea coast, and the Herminones, living inland of these groups.
In linguistics, the term "Istvaeonic languages" is also sometimes used in discussions about the grouping of the northwestern West Germanic languages, consisting of Frankish and its descendants (principally Old Dutch) as well as several closely related historical dialects. Whether or not the Istvaeones spoke a Germanic language according to modern definitions, the theory proposes that their language indirectly influenced later Germanic languages in the area as a substrate.
The term Istvaeonic is derived from a culturo-linguistic grouping of Germanic tribes mentioned by Tacitus, who used the spelling "Istæuones" in his Germania, and Pliny the Elder, who used the spelling "Istuaeones". Pliny further specified its meaning by claiming that the Istævones lived near the Rhine. Jacob Grimm in the book Deutsche Mythologie argued that Iscaevones was the correct form, partly because it would connect the name to an ancestor figure in Norse mythology named Ask and partly because in Nennius where the name Mannus is corrupted as Alanus, the ancestor of the Istaevones appears as Escio or Hisicion.
The Istvaeones (Pliny) or Istaevones (Tacitus) are therefore one of the least clearly defined of these groups, but Pliny and Tacitus and other classical sources clearly associated various tribes the Rhine frontier region, and the description of Pliny also explains that the Chatti, Cherusci and Chauci are not included in the group. In this period, between them and the Rhine, Tacitus also specifically named various tribes such as the Chamavi, Bructeri, Sugambri, Ubii and others. Also by implication the definitions above include all of the Romanized Germani Cisrhenani on the Roman side of the Rhine, because Tacitus (and before him by Julius Caesar) agreed that these peoples were related to the Germanic tribes on the other side of the Rhine. Tacitus mentions that in his time they called themselves the Tungri. He also mentions that some Rhine tribes by his time, such as the Batavi, and Cananefates, were in fact in recent immigrants, and relatives of the Chatti. Throughout the Roman era, starting already in the time of Caesar, more eastern Germanic tribes pressed the Rhine area, most famously the Chauci, Saxons and Suevians, pushing tribes into the area such as the Usipetes, Tencteri and Ampsivarii. Despite the pressures from two directions, the Chamavi and Bructeri survived in the same area until late Roman times, along with various tribes who may have been there in the time of Tacitus, or may have immigrated, such as the Salii and Chattuari (whose name suggests a connection to the Chatti).
The historical sources give no complete account of the Istvaeones. Modern historians attempt to extrapolate their tribal constituents based on later sources, archeological findings and linguistic information.
There is an overlap between Germanic tribes generally assumed to have been Istvaeonic in terms of dialect and culture, and the tribes who came later to be thought of collectively as the earliest "Franks". Edwards (1988, p. 35) speculated that the Chamavi may have been the first such tribe, around which neighbours came also to be called by this name:
The large "Irmionic" nation of the Chatti also seem to have been considered Franks, or allies of the Franks, at least once. In one of the last mentions of them as a separate people, Sulpicius Alexander, cited by Gregory of Tours mentions them as being led along with the Ampsivarii by the Frankish king Marcomer.
The Salii were first mentioned as a Frankish tribe from north of the Rhine, from near the Chamavi. (Their origins before then are not known.) They were allowed to move into Roman territory, starting with the delta island of Batavia, and then Toxandria. In the 5th century, in the time of Flavius Aëtius they conquered as far as Tournai, despite Roman opposition, and later worked with the Romans against Attila the Hun. Further up the Rhine, the Ripuarian or Rhineland Franks (Latin Ripuarii, a name associated with the Latin word for "river") eventually had a kingdom centred upon the Roman-founded city of Cologne, on the left bank of the Rhine. The Chattuari also apparently crossed the Rhine and held lands on both sides, in an area between the Salians and Ripuarii (and possibly under the lordship of one or both of them). A separate Chamavi population possibly still existed as late as the 8th century, when it has been proposed that a Chamavi legal code was published under Charlemagne, the so-called Lex Chamavorum.
During the late 5th century, the Frankish frontier tribes and the Roman territories of Northern Gaul came to be politically united under a Frankish military leader of northern Roman Gaul, and "King of the Franks" Clovis I, and his Merovingian dynasty. This Frankish kingdom of northern Gaul published a Salian legal code applicable to the Roman region south of the original Salian territories, from the Loire in modern France to the Silva Carbonaria in modern Belgium. It grew to rule large parts of the former Western Roman Empire and Germania.
At some point in the above sequence, the ethnonyms "Frank" and "Frankish" morphed into a term closer in meaning to a proto-state or political identity, rather than a tribal or ethnic designation and can no longer be considered synonymous with the Istvaeones. (However from the Merovingian period it is clear, as for example reported by Gregory of Tours, that there was a "Frankish language" distinct from the Romance languages which continued to be spoken by much of the population in what would become France.)
The German linguist Friedrich Maurer (1898–1984), in his book "Nordgermanen und Alemannen", used the term Istvaeones to refer to a unattested proto-language, or dialectal grouping, ancestral to Old Frankish, Old Dutch and, at the very least, influenced several dialects of West Central German.
Finds assigned to the Istvaeones are characterized by a greater heterogeneity than can be found in the other Germanic archaeological groupings. Their predominant burial type is the pyre grave. There are no richly equipped princely graves or weapons as grave goods to be found as, for example, occur with the neighboring Elbe Germanic groups. Scholars have speculated about whether weapons were used as "immaterial" grave goods instead. In other words, weapons made of metal were placed on the pyre of a warrior, for example, but only his ashes were buried in the pyre grave. This is, however, a controversial thesis. Weapons as grave goods first appear in northern Gaul, i.e. on the Roman side of the Rhine, in burial graves, and are not found to the east of the Rhine until the Merovingian period.