Megavitiornis altirostris is an extinct, flightless, giant stem-galliform bird that was endemic to Fiji, it is the only known species in the genus Megavitornis. Originally thought to be a megapode, more recent morphological studies indicate a close relationship with Sylviornis of New Caledonia, in a clade outside of the Galliformes crown group. It is likely that it became extinct through overhunting shortly after the colonisation of the Fiji Islands by humans.