The writing on the One Ring in Lord of the Rings is actually written in the Black Speech of Mordor using the fictional script Tengwar (example pictured).
An English translation of the inscription is as follows:
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
The inscription on the One Ring can only be seen after the ring has been submerged in fire; most of the time, it looks like a plain gold ring.
Why Does It Say That?
The lines written on the One Ring are taken from the spell that gave all the rings their power in the first place, and also form part of a poem about the lore of their creation:
Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the Land of Mordor where the Shadows lie.
