Treebeard is the talking tree-like being who helps Merry and Pippin in The Lord of the Rings: The Two Towers.
Treebeard is an Ent, an ancient shepherd of trees who lives in Fangorn Forest. After meeting Merry and Pippin, he learns how Saruman’s industrial expansion is destroying the forest and eventually leads the Ents against Isengard.
The film presents Treebeard through a combination of performance and visual effects. He is voiced and performed by John Rhys-Davies, who also plays Gimli, although the two characters have very different voices and physical designs.
Treebeard is sometimes confused with Quickbeam, another Ent seen in the film. Old Man Willow is a separate tree-like character from Tolkien’s wider legendarium and is not the Ent who leads the assault on Isengard.