Mecistocephalus siaronus is a species of centipede in the Mecistocephalidae family.

It was described in 1920 by American myriapodologist Ralph Vary Chamberlin.

[1][2] This species has 49 pairs of legs and can reach 90 mm in length.

[1] The species occurs in Fiji.

The type locality is Saiaro, Viti Levu.