The Huorns are fictional characters from J. R. R. Tolkien's Middle-earth legendarium. They are described as "trees" that can speak to Ents and are capable of locomotion.
Tolkien's character Treebeard describes both Ents that become tree-ish, and trees that become Entish. Meriadoc Brandybuck believed Huorns to be the former, although Treebeard would not say much about them. Huorns can create darkness to conceal their movements and are capable of moving quickly and quietly. They still have voices and can speak to the Ents, but unlike Ents, they do not seem able to speak intelligibly to other races.
According to Treebeard, Huorns have become queer, wild and dangerous. They watch over the trees but are in turn looked over by Ents. Merry believes there are hundreds and hundreds of them in the darkest dales of Fangorn forest. It is possible that some of the trees of the Old Forest, especially Old Man Willow, were Huorns as well. Both forests were once parts of the same primeval forest (Forests of Eriador). A connection is implied by Treebeard's statement in response to Merry's question as to whether the Old Forest was similar to the dark spots of Fangorn forest:
"Aye, aye, something like, but much worse. I do not doubt that there is some shadow of the Great Darkness lying there still away north; and bad memories are handed down. But there are some hollow dales in this land where the Darkness has never been lifted, but the trees are older than I am."
Huorns could have existed as far back as the First Age when the Ents appeared. They make their first appearance in The Two Towers when they take part in the Last March of the Ents and participated in the Destruction of Isengard and the Battle of the Hornburg, destroying all orcs trying to escape the battles.
Huorn is the name in the "short-language" of the Ents, given because the Huorns "still have voices". It includes the Sindarin noun orn which means "tree". The meaning of the hu element is unknown, Tolkien himself seemed unsure. In the Huorn entry in a wordlist published in Parma Eldalamberon Tolkien gives the possible Sindarin roots hô, hyoba and hû. The description of hô could be interpreted "speak, show" which would correspond with the earlier names for Huorns in The War of the Ring which all meant "talking trees".
In the MMORPG computer game The Lord of the Rings Online: Shadows of Angmar, huorns can be found in the Old Forest, Lone-Lands, Eregion, and the Ettenmoors. They appear as twisted trees, with roughly eye-shaped crevasses in their trunks. Some of the huorns, particularly in Angmar, are so motionless and tree-like as to resemble harmless scenery on higher graphics settings, a danger for the unwary player.
In the 2003 RTS game The Lord of the Rings: War of the Ring, huorns are a special unit that can only be summoned from a Nature's Haven while you play as the Good side. They are normally a good counter to trolls in the game. The huorns in this game look like trees with two legs and two arms. Their tops are surrounded by flying leaves; the leaf color indicates the team to which the huorn belongs. They attack with their arms in swift strikes.