Mandos is a fictional character from J. R. R. Tolkien's universe, Middle-earth.

Mandos is the usual name for the Vala originally called Námo (Judge). Námo was given this new name in honor of the Halls of Mandos, over which he presides, where Elves go after they are slain (cf. Valhalla). His wife is Vairë the Weaver, and he is the brother of Lórien and Nienna in the mind of Ilúvatar.

Mandos is described as being stern and dispassionate and never forgetting a thing. He was the Vala who cursed the Ñoldor leaving Aman, and counselled against allowing them to return (almost to the point of vindictiveness). But unlike Morgoth, his Dooms are not cruel or vindictive by his own design. They are simply the will of Eru, and he will not speak them unless he is commanded to do so by Manwë. Only once has he been moved to pity, when Lúthien sang of the grief she and her lover Beren had experienced in Beleriand. Then with the Elder King's approval, he released them.

In the roguelike computer game ToME the Halls of Mandos are location of a preliminary lost soul nightmare mode for experienced players.