Weasels are among the most widespread small carnivores, playing a key role in extant Holarctic ecosystems by preying on other small vertebrates. Despite their substantial diversification during the Pleistocene, the evolutionary origins of these species before this period remain poorly understood. The most widely accepted view is that the oldest known true weasel, Mustela, dates from the Pliocene (4-3.5 Ma) of central Europe. A newly discovered species of a weasel-like mustelid, Galanthis baskini gen. et. sp. nov. from Las Casiones (Spain), demonstrates a Late Miocene (6.56-6.26 Ma) origin for Mustelinae, which is consistent with molecular divergence estimates for Mustelinae. Galanthis baskini emerges as the most basal member of the subfamily, confirming a small size (134.55 g) from the beginning of its evolutionary history. These findings shed light on the early evolution of Mustelinae and show that small forms already existed in the Late Miocene. In addition, Proputorius minimum, a related mustelid from China, is reclassified as Zdanskyictis gen. nov., which is closely related to the subfamilies Lutrinae and Ictonychinae. Galanthis and Zdanskyictis highlighting the key role of Eurasia in the evolution of the Mustelidae during the Miocene.