The Hessel is a 40 kilometres (24.9 mi) long, right tributary of the River Ems in the territory of the North Rhine-Westphalian districts of Gütersloh and Warendorf in northwest Germany.

The river rises northwest of Halle (Westf.) on the Große Egge, crosses the Hermannsweg, flows through the villages of Hesseln and Hörste in Halle borough, then through the borough of Versmold

Versmold

Versmold is a town in Gütersloh District in the German state of North Rhine-Westphalia. It is located some 30 km west of Bielefeld.- History :...

 through Oesterweg, continuing through the town of Sassenberg

Sassenberg

Sassenberg is a town in the district of Warendorf, in North Rhine-Westphalia, Germany. It is situated approx. 6 km north-east of Warendorf and 30 km east of Münster....

 and along the southern edge of Milte in the borough of Warendorf

Warendorf

Warendorf is a town in North Rhine-Westphalia, Germany, and capital of Warendorf District.The town is best known today for its well-preserved medieval town centre, for horse-riding, and the opportunities it provides for cycling...

, before emptying into the Ems near Warendorf-Einen.

Tributaries include the Casumer Bach

Casumer Bach

Casumer Bach is a river of North Rhine-Westphalia, Germany....

, Bruchbach, Aabach

Aabach (Hessel)

Aabach is a river of North Rhine-Westphalia, Germany....

, Poggenfahrtgraben, Sandfortbach, Teichwiese, Wöstenbach, Beckstroth, Arenbecke and the Speckengraben.

The Snake's Head Meadows lie along the Hessel near Sassenberg, one of the few areas in Germany in which this strictly protected wildflower occurs.