This is a probably a Roman copy of the god of war Ares. The sculptor Alkamenes is known to have made a statue of Ares that stood in the Athenian Agora, but to connect this sculpture with that is speculation.

However as Ares was rarely depicted in art and sculpture, it may represent Achilles; the helmet and (restored) spear in the left hand could be attributes of either. It has also recently been proposed that the sculpture was a Roman original created through Augustan propaganda to cast Augustus’s heir and grandson, Gaius, as “the New Ares”