Ringworlds are hypothetical space megastructures that typically represent some form of habitat in the form of a ring. Often these rings will spin, generating the centrifugal force necessary to hold people and objects onto their inner surface.
If the Ringworld surrounds a star, it may also be considered a Dyson Ring. If this is the case, worldbuilders may want to remember that Ringworlds are unstable, and without some way to correct or maintain their location in space, any Ringworld will likely drift and eventually collide with its’ central sun.
As with all megastructures, when incorporating Ringworlds into your fictional world, consider the purpose for which it was built, who built it, and where the materials for such a vast construction project originated.
A Ringworld is also known as a Niven Ring, after science fiction author Larry Niven who wrote several books about such a structure.