Tonna is bounded by the wards of Aberdulais to the north; Resolven to the northeast; Pelenna to the southeast; Cimla and Neath North to the southwest; and Cadoxton to the west.
Tonna is delimited by the wards of Aberdulais to the north; Resolven to the northeast; Pelenna to the southeast; Cimla and Neath North to the southwest; and Cadoxton to the west.