Nelkar is a Class M planet located in Sector 221-G . It is the homeworld of the Nelkarites, with its capital city is Selinium. Following the collapse of Thallonian Empire, a number of refugees settled on Nelkar. (NF novels: The Two-Front War, End Game)

Doctor Meron Byxthar, a sociological expert, observed the life of the Thallonians on Nelkar as part of her work. (TNG novel: Losing the Peace)

planets visited by ships named Excalibur
USS Excalibur (2240s)	Donatu V
USS Excalibur (NCC-1664)	Velarrh VII • Linyar II • Altair VI • Neural III • Priatia • Argelius II
USS Excalibur (NCC-26517)	Vigan Delta V • Lintar IV • Argelius II • Nelkar • Thallon • Zondar • Ahmista • Haresh • Enev • Narobi II • Fennar
USS Excalibur (NCC-26517-A)	Priatia