Firefighters have been called to reports of a blaze in Greno Woods in Sheffield.
The fire in Grenoside was reported at 12.05pm and firefighters at the scene said a large area of bracken and woodland is on fire.
There are three fire engines at the scene.
Greno Woods is a 178 hectare site, managed by Sheffield Wildlife Trust, which boasts over 60 species of birds.
The ancient woodland dates back to 1600AD.