The species occurred across Europe and western Asia. Ireland is over-represented in collections because its bogs preserve bone unusually well and because a lake-margin habitat there concentrated remains, not because the animal was Irish in any meaningful sense. Late specimens from the Ural region date to around seven to eight thousand years ago, well into the Holocene.
On relationships, morphological and molecular evidence places Megaloceros closest to the fallow deer, genus Dama, rather than to the moose, Alces alces, which North Americans call elk, or to the red deer, which Europeans call elk in some translations. The name is a double misnomer.
The antlers, spanning up to roughly 3.6 metres and weighing tens of kilograms, once prompted the idea that the species was doomed by runaway ornament growth. That explanation has been discarded. Antler size scales predictably with body size across deer, and the extinction is now attributed to vegetation change after the Younger Dryas reducing the mineral-rich forage needed to grow antlers each year, with hunting pressure as a possible additional factor.