The Elvish name for the long, narrow range of peaks more commonly called the Misty Mountains. The name Hithaeglir is usually translated 'Towers of Mist', though it actually contains the Elvish word aeglir, meaning a range of sharply pointed peaks. The mountains of the Hithaeglir did indeed rise to notably sharp peaks, and had been even more forbidding in ancient days. According to legend they had been raised in an arc across Middle-earth by Melkor to hinder the Vala Oromë in his ridings into the eastern lands.

In that purpose Melkor failed: despite the Mountains, Oromë was able to travel into the far East of Middle-earth and discover the newly awakened Elves. A great part of these Elves he persuaded to accompany him back to the Blessed Realm in the West, but on coming to the high, sharp peaks of the Hithaeglir, the hearts of many of the Elves were filled with terror. These people fell away from the Great Journey, settling in the Vales of Anduin as the Nandor, from whom the Silvan Elves of Lórien and Mirkwood would spring.

After this division of the Elves, the histories of the First Age were recorded by those who had passed the Hithaeglir and travelled on to Beleriand and across the Great Sea. From their perspective, the great mountain range became part of their distant history, and is rarely mentioned in their accounts of those times. Even these people, though, were aware of a great city that arose among the Hithaeglir, a city of the Dwarves that the Elves called Hadhodrond (a name derived from its Dwarvish name of Khazad-dûm).

In texts from later ages the old Elvish name Hithaeglir is seen far less often, and this range is almost universally referred to as simply the 'Misty Mountains'. We do, however, have some evidence of the mountains being named Hithaeglir from time to time throughout the Second and Third Ages. In the Second Age, in a letter sent to King Tar-Meneldur of Númenor, Gil-galad referred to the Hithaeglir, describing them as his people's major defence against the forces that were stirring farther east. Millennia later, the name was used by Steward Cirion of Gondor in his Oath that granted the land of Calenardhon to Eorl and his people, and thus created Rohan. Both these examples come from highly formal uses of the Elvish language, though as the normal Elvish form of the name 'Misty Mountains', the term Hithaeglir also seems likely to have remained in common use among the speakers of that language.