Nassau is a former Verbandsgemeinde ("collective municipality") in the Rhein-Lahn-Kreis, in Rhineland-Palatinate, Germany. In January 2019 it was merged into the new Verbandsgemeinde Bad Ems-Nassau. Its seat was in Nassau.

The Verbandsgemeinde Nassau consisted of the following Ortsgemeinden ("local municipalities"):

Attenhausen Dessighofen Dienethal Dornholzhausen Geisig Hömberg Lollschied Misselberg Nassau Obernhof

Oberwies Pohl Schweighausen Seelbach Singhofen Sulzbach Weinähr Winden Zimmerschied

50°19′01″N 7°48′00″E / 50.317°N 7.800°E / 50.317; 7.800