Although all German states (including Prussia) had been de facto dissolved since 1933, the Nazi government formally partitioned the Prussian province of Hesse-Nassau into two provinces with a decree issued on 1 April 1944 and effective on 1 July 1944.

The name comes from the former Duchy of Nassau (1806–1866), which Prussia annexed following the Austro-Prussian War to form part of the province of Hesse-Nassau.

The territory of the province was larger than that of the former duchy, encompassing those areas of the NSDAP Gau Hesse-Nassau not part of the People's State of Hesse.

Following the end of World War II, most of the province of Nassau fell under American administration.

A small western part of the province of Nassau instead fell under French control; it became the Regierungsbezirk Montabaur of the modern state of Rhineland-Palatinate on 30 August 1946.