Around 45 firefighters and eight engines tackled the grassfire blaze on the mountain above Godre’r Graig in the Swansea Valley on Tuesday.
The fire began around 8am before spreading across 176 hectares of grass, gorse and forestry which were destroyed.
Emergency services believe the fire was started deliberately and urge people with information to call the police.
The total number of grass fires dealt with by South Wales Fire and Rescue Service are up by nearly 200% on last year, new figures show.
More than 100 blazes across Rhondda Cynon Taf and Merthyr Tydfil have been reported to police since the beginning of March.
People starting grass fires should be locked-up Wales' Public Services Minister will be told later today