The remains of the largest Hoplitomeryx known to date have been retrieved from the upper Miocene limestones of Scontrone (Abruzzo, central Italy). Hoplitomerycidae derived from small-sized Oligocene Tragulina ruminants. Therefore, this is the first giant insular ruminant ever described. Insular giantism has been notoriously exhibited by other taxa, such as rodents. It is suspected for the largest Cretan deer Candiacervus, if these cervids monophyletically are derived from Dama. This large Hoplitomeryx was a lightly built animal with long, slender limbs. This case shows not only that insular giantism can be attained also on large islands, but confirms that it can be promoted by competitive release and immigrant selection.