Onhaye is a Walloon municipality located in the Belgian province of Namur. On January 1, 2006, Onhaye had a total population of 3,120. The total area is 65.53 km² which gives a population density of 48 inhabitants per km².
The municipality consists of the following sub-municipalities: Onhaye proper, Anthée, Falaën, Gerin, Serville, Sommière, and Weillen.
The region is home to several cultural heritage monuments, such as Château de Fontaine and the fortified farmhouse Falaën Castle.