The Alsenz () is a river in Rhineland-Palatinate, Germany, a right tributary to the Nahe. It rises in Enkenbach-Alsenborn, north-east of Kaiserslautern, flows generally north, and joins the Nahe in Bad Münster am Stein-Ebernburg. Its length is roughly . Towns along the Alsenz include Winnweiler, Rockenhausen and Alsenz.