A fairy ring takes the form of a circular or semi-circular formation of mushrooms or an unusually lush, dark green patch of grass and can damage your lawn's health and aesthetics.
Regular watering, fertilizing, and aeration of your lawn help maintain its overall health, but it will also help visually minimize the fairy ring visually by camouflaging it.
If the fairy ring is causing dying grass or other damage, you could excavate the affected lawn area, extending to about 300mm inside it, and replace it with fresh soil.
Fungicide treatment should be used as a last resort because their chemicals can hurt the environment and target fungi and other microorganisms that are beneficial to your lawn.