Nar'el was an inhabited planet and the homeworld of a pre-warp civilization.
In 2248, Captain Robert April of the USS Enterprise sent his science officer to Na'rel, then at an industrial age degree of development, to solve the threat of an extinction-level drought by sharing Federation technology, in violation of the Prime Directive.
During Una Chin-Riley's court martial in 2259, Neera Ketoul cited the Na'rel incident as an example of when a Starfleet captain had exercised their judgment over the application of law for the greater good. (SNW: "Ad Astra per Aspera")
This planet was only mentioned in dialogue.