Arnor was a kingdom in the fictional world of Middle-earth, created by author J.R.R. Tolkien. It was established by the Dúnedain after the fall of Númenor and was located in the northern part of Middle-earth, primarily in what is now known as Eriador. The kingdom was divided into three main regions: Arthedain, Cardolan, and Rhudaur. Arnor faced many challenges, including internal strife and external threats from enemies like the Witch-king of Angmar. Eventually, the kingdom fell, leading to the rise of the Rangers of the North, who were its descendants.