The Sunuci (or Sinuci or Sunici) was the name of a tribal grouping with a particular territory within the Roman province of Germania Inferior, which later became Germania Secunda. Within this province, they were in the Civitas Agrippinenses, with its capital at Cologne. They are thought to have been a Germanic tribe, speaking a Germanic language, although they may also have had a mixed ancestry. They lived between the Meuse (Dutch Maas, Latin Mosa) and Rur rivers in Roman imperial times. In modern terms this was probably in the part of Germany near Aachen, Jülich, Eschweiler and Düren, and the neighbouring areas in the southern Netherlands, around Valkenburg, and eastern Belgium, in part of the old Duchy of Limburg. There is a town just over the Belgian border from Aachen called Sinnich, in Voeren, which may owe its name to them. In other words, they lived just north of the modern northern limits of Romance languages derived from Latin.
The origins of the tribe are unknown, but it is likely that, like their eastern neighbours the Ubii, their ancestry included Germanic immigrants from the east of the Rhine who had been arriving for generations. Like the Cugerni for example, they may descend from Sicambri. Germania Inferior was on the west of the Rhine and had been described by Julius Caesar, at the time of Roman conquest of the area, as part of Belgic Gaul. Many of the tribal names and personal names which he reported from this area, are considered to be Celtic, not Germanic. However already long before his time there appears to have been an influx of people coming from the east of the Rhine, including, in the particular area where the Sunuci lived, the tribal grouping which Tacitus later claimed to be the original tribal group which had been called "Germani", the so-called "Germani Cisrhenani". Whether these original Germani had all spoken a Germanic language is unknown. Caesar and Tacitus were more interested in the fact that tribes from the east of the Rhine, who all eventually came to be referred to as Germani (the source of the modern word "Germany"), and all eventually came to speak a Germanic language, were less softened by civilization, and therefore difficult to defeat in battle or incorporate into the Roman empire.