This comprehensive checklist of non-marine molluscs from the mainland of Ecuador presents data on 331 species (of which 5 are considered as nomen dubium), compiled from the literature, a subset of museum databases, and some verified observations from the internet. For all taxa the original reference is given and photographs of type specimens are provided if these could be located and obtained from museums. Where these were not available the original figure(s) have been reproduced. In the introduction, a brief history of research in Ecuador (including the Galápagos archipelago) is presented. This checklist may serve as a baseline document for further research. It is not intended to be a revisionary work, although we have recognised the following new synonyms: Neritina intermedia (var. β) minima K. Miller, 1879 = Clypeolum latissimum (Broderip, 1833); Aperostoma (Aperostoma) olivaceum Bartsch & Morrison, 1942 = Incidostoma quitense (L. Pfeiffer, 1852); Hemisinus pazi Tryon, 1866 = Hemisinus guayaquilensis (Petit de la Saussaye, 1853); Bulimus cuneus L. Pfeiffer, 1854 = Protobeliscus fairmaireanus (Petit de la Saussaye, 1853); Synapterpes (Zoniferella) riveti Germain, 1907 = Mesembrinus vesperus Jousseaume, 1887 = Zoniferella albobalteata (Dunker, 1882); Synapterpes bicingulatus Fulton, 1908 = Zoniferella bizonalis (Germain, 1907); Thaumastus thompsonoides Oberwimmer, 1931 = Kara thompsonii (L. Pfeiffer, 1845). The need for further field work is illustrated by the fact that for 60 species, only imprecise localities are known, while for 168 species no modern (i.e. last 50 years) records are available. There are 178 species considered as endemics for the Ecuadorian malacofauna. For both the terrestrial and freshwater species the ecoregions where they occur are indicated where possible.