Sylviornis is an extinct genus of stem-galliform bird containing a single species, Sylviornis neocaledoniae, or erroneously, "New Caledonian giant megapode". Technically, the latter is incorrect because it has recently been found not to be a megapode, but one of two genera in the family Sylviornithidae; at the time of its description it was believed to be a ratite. Sylviornis was never encountered alive by scientists, but it is known from many thousands of subfossil bones found in deposits, some of them from the Holocene, on New Caledonia and the adjacent Île des Pins. Recent morphological studies indicate that it was a sister taxon of Megavitiornis, in a clade outside of the Galliformes crown group.