The Nordwestblock (English: "North-West Block"), is a hypothetical cultural region, that several 20th century scholars propose as a prehistoric culture, thought to be roughly bounded by the rivers Meuse, Elbe, Somme and Oise (the present-day Netherlands, Belgium, northern France and western Germany) and possibly the eastern part of England during the Bronze and Iron Ages (3rd to 1st millennia BC, up to the gradual onset of historical sources from the 1st century).

The theory was first proposed in 1962 by Rolf Hachmann, an historian, Georg Kossack, an archeologist, and Hans Kuhn, a linguist. They continued the work of the Belgian linguist Maurits Gysseling, who got his inspiration from the Belgian archeologist Siegfried De Laet. Gysseling's original proposal included research that another language may have existed somewhere in between Germanic and Celtic in the Belgian (sic) region.

The term itself Nordwestblock was coined by the German linguist, Hans Kuhn, who considered the inhabitants of this area neither Germanic nor Celtic, thus attributing to the people a distinct ethnicity or culture. According to Kuhn and his followers, the region was Germanised from the beginning of the Common Era, at the latest.