The Kleine Dommel, also known as the Rul, is a brook approximately 11 kilometers in length flowing through the Campine and Meierij van 's-Hertogenbosch region of the Netherlands. It originates near Heeze Castle and flows to its mouth at Eckartdal, west of Nuenen, where it joins the Dommel. The river drains a basin of around 210 square kilometers. Discharge varies considerably by season, averaging roughly 1 cubic meter per second in summer and rising to approximately 3.5 cubic meters per second in winter, measured at the A67.

The stretch between the Eindhovensch Canal and the Watermill at Kollen passes through a nature reserve called Urkhovense Zeggen, a protected area of about 180 hectares that includes the Collse Zeggen, Hulsterbroek, and Varkensput. Roughly 70 hectares of this reserve are owned by the municipality of Eindhoven. The area contains a type of mesic grassland vegetation known as blauwgrasland, a rare habitat of which only 60 hectares remained in the Netherlands as of 2016. The reserve has been under protection since 1970 due to the presence of wild orchid species.

A notable landmark along the river is the Watermill at Opwetten, which features the largest water wheel in the Netherlands. The gristmill remains operational and is typically run on Sundays. The mill's history is documented back to the 11th century, though the current buildings date from the 18th century. A former oil and fulling mill on the same site now operates as a restaurant. The Watermill at Opwetten was also the subject of a painting by Van Gogh.

The river's character is shaped by its passage through protected natural areas and its association with historic mill sites, making it a route of both ecological and cultural interest. The significant difference in water levels between summer and winter is a practical consideration for trip planning, as lower summer flows may affect navigability along certain sections.