The Abercarn colliery disaster was a catastrophic explosion within the Prince of Wales Colliery in the Welsh village of Abercarn (then in the county of Monmouthshire), on 11 September 1878, killing 268 men and boys (though an exact number of casualties remains unknown). The cause was assumed to have been the ignition of firedamp by a safety lamp. The disaster is the third worst for loss of life to occur within the South Wales Coalfield.