We describe a new insular endemic lagomorph from the Late Neogene karstic deposits of Minorca (Balearic islands, Spain). Nuralagus rex, gen. et sp. nov., is characterized by an array of odd traits unknown for lagomorphs. Most outstanding are the gigantic size (average 12kg), the robust postcranial skeleton with unique morphological traits (short manus and pes with splayed phalanges, short and stiff vertebral column with reduced extension/flexion capabilities), and the relatively small size of sense-related areas of the skull (tympanic bullae, orbits, braincase, and choanae). These morphological traits denote an important decrease in locomotor and neurological activities and, hence, a decrease in metabolic energy expenditure, which is concordant with the ecological conditions of the insular environment characterized by absence of predators and low levels of resource supply. Our discovery enhances the importance of the frequently neglected fossil record for our understanding evolution on islands, because it provides the perspective of time and adds valuable data from fossil insular ecosystems unaffected by anthropogenic alterations. © 2011 by the Society of Vertebrate Paleontology.