Gronau (German pronunciation: [ˈɡʁoːnaʊ] ⓘ) is a river of Hesse, Germany and a right tributary of the Sinn.

Including its left source river Westernbach, it has a total length of 9.7 kilometres (6.0 mi).

[1] The Gronau rises in the unincorporated area Gutsbezirk Spessart in the Hessian part of the Mittelgebirge Spessart.

It flows into the Sinn at Altengronau.

This article related to a river in Hesse is a stub.