Treebeard is the Ent who guards the gardens of Isengard in Tolkien’s fiction.
Treebeard, whose Sindarin name is Fangorn, is one of the oldest beings in Middle-earth. He appears in The Two Towers, the second volume of The Lord of the Rings, where Merry and Pippin meet him in Fangorn Forest. The Ents are tree-like shepherds responsible for protecting the forests and their trees.
Treebeard initially distrusts the hobbits because he believes they may be Orcs, but he eventually listens to their account of Saruman’s destruction of the forests. He calls an Entmoot, or gathering of Ents, and the Ents march against Isengard. Their action helps overthrow Saruman’s power in the region.
Quickbeam is another Ent, while Beorn is a shape-shifter from The Hobbit. Tom Bombadil is an ancient figure, but he is not an Ent and is not the guardian of Isengard’s gardens.