Tilff (in Walloon Tif) is a section of the Belgian municipality of Esneux located in the Walloon region in the province of Liège.
It was a municipality in its own right before the 1977 municipal merger.
The village is located about ten kilometers south of Liège in the Ourthe valley at the northern limit of Condroz and more precisely in the Ardennes Condrusian sub-region as well as to the north-west of Calestienne. The river crosses it from south to north. The lowest point is the bottom of the valley (70 m in Sainval).
Its soil is largely karstic. Several chantoires can be observed, especially in the Bois des Manants, where "Li Tchawresse" flows, a 3.5 km stream that ends its course in a chantoire and reappears several kilometers downstream before flowing into the Ourthe. The valley is classified as a “protected natural site”. The hill is carved out of multiple caves and caverns, of varying sizes (Sainte-Anne cave, Nutons hole, Manants hole).
The heights of Tilff form, on the right bank, the hamlet of Tilff-Cortil (from the Walloon “Corti”, the garden) and on the left bank, the hamlet of Sur-le-Mont, which adjoins the University campus from Liège to Sart-Tilman.