The Paleontological Collection of Tübingen University houses one of the largest collections of ichthyosaur specimens from the Lower Jurassic (Lower Toarcian) Posidonienschiefer Formation fossillagerstätte in the world. It forms an important basis for numerous past and ongoing studies on the taxonomy, evolutionary morphology, ecology, and other aspects of ichthyosaur biology. The collection includes particularly significant material, such as several type specimens, representatives of rare species, and different ontogenetic stages, which show varying degrees of preservation. Founding fathers of paleontology at Tübingen University, including Friedrich August Quenstedt (1809–1889) and Friedrich v. Huene (1875–1969), assembled the majority of these specimens and conducted extensive research using Tübingen ichthyosaurs. Many more recent publications also use Tübingen material as a reference. Unfortunately, in many cases the identity and provenience of old museum specimens are not adequately known. This has led to confusion, inconsistencies, and errors in the literature. Here we present a detailed assessment of the history and identity of the ichthyosaurs from the Posidonienschiefer Formation in the Tübingen collection by conducting both a comprehensive literature survey and a re-investigation of the entire collection. We consulted document archives and critically compared them to hand-written specimen labels. In total, we were able to clearly identify and illustrate 78 articulated specimens that are now fully accessible for international researchers with clear documentation of their stratigraphical allocation. With respect to old natural history collections in general, we provide a broader discussion on how to deal with historical specimens (which sometimes represent composites of several individuals) and identify a series of challenges when dealing with confusing documentation. Our study attempts to provide means to solve these issues to facilitate and provide a more reliable database for future research.