Twelve Olympians
Though not all the gods who appear in Rick Riordan's novels are truly "Olympians" (that is, gods who live on Mount Olympus), all Greek and Roman gods are generally considered to be a subset of the Twelve Olympians. As such, most characters in the series refer to these immortals generally as the "Olympian gods", to distinguish them from the Greco-Roman primordial gods and Titans.