Weser–Rhine Germanic languages (or Rhine–Weser Germanic, German: Rheinweser-germanisch), sometimes also referred to as Istvaeonic languages, are a proposed Frank-related subgroup of the West Germanic languages which would in terms of modern languages unite both West Central German dialects and Low Franconian dialects including standard Dutch.
According to original versions of this proposal, introduced by the German linguist Friedrich Maurer (1898-1984), this subgroup descends from a distinct Frankish language, while the related ancestral languages of the so called Elbe Germanic dialects to the south, and North Sea Germanic languages to the north, only subsequently became smoothly connected within the same dialect continuum. Maurer's proposals were influenced not only by linguistic evidence, but also by the Germanic archaeological provinces defined by Raphael von Uslar in 1938, which include the so called Rhine-Weser Germanic peoples, and by early Roman era reports of the Istvaeones – a group of Germanic peoples which lived near the River Rhine, and understood themselve to share a distinct common ancestry, according to their descriptions by Tacitus and Pliny the Elder.
