The common moorhen, also known as the waterhen, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World, across Africa, Europe, and Asia. It lives around well-vegetated marshes, ponds, canals and other wetlands. The species is not found in the polar regions or many tropical rainforests; generally it is one of the most common Old World rail species, together with the Eurasian coot in some regions.