The Mornan was a dark valley in the White Mountains where the spring of the source of the Morthond was located.
The Mornan was a dark and narrow valley that lay beneath the shadow of two high mountains in the Ered Nimrais, being located directly to the south of Edoras. Above the Mornan was a hidden gateway within some shadowed rocks which lead out from the Gate of the Dead Men.
On 8 March T.A. 3019, Aragorn, Gimli, Legolas, and the Grey Company exited the Paths of the Dead at the Mornan. They rode to the Stone of Erech where Aragorn, as the heir of Isildur, called upon the Oathbreakers to follow him and fulfill their pledge.