We describe the prehistoric bones of Gallirallus spp. from 14 prehistoric sites on seven islands in the Kingdom of Tonga, South Pacific. Two specimens (tibiotarsi) from Ha'afeva (Ha'apai Group) probably represent an extinct species but are considered to be an inadequate basis for description. Otherwise, all bones from cultural sites (<3000 years old) are referred to the extant G. philippensis, which is widespread in Oceania today. From an older site on ‘Eua Island, we describe a new extinct species, G. vekamatolu. Qualitative osteological characters, as well as multivariate statistical analysis of hind-limb and forelimb measurements, indicate that this new species was flightless. On ‘Eua, G. vekamatolu is the only rail recorded from pre-cultural strata, whereas three extant volant species of rails (G. philippensis, Porzana tabuensis, Porphyrio porphyrio) are recorded from strata that post-date human arrival. Gallirallus vekamatolu is the third flightless species of Gallirallus described from prehistoric sites in tropical Polynesia. It adds to the growing list of Pacific island birds that went extinct after human colonization.