I'll just carve this one right out of Wikipedia:
Ents are a race of beings in
J. R. R. Tolkien's
fantasy world
Middle-earth who closely resemble
trees. They are similar to the
talking trees in folklore around the world. Their name is derived from the
Anglo-Saxon word for
giant.
The Ents appear in
The Lord of the Rings as ancient shepherds of the forest and allies of the free peoples of Middle-earth during the
War of the Ring. The Ent who figures most prominently in the book is
Treebeard, who (credibly) claims to be the oldest creature in Middle-earth. At the time
The Lord of the Rings takes place, there are no young Ents (Entings) because the Entwives (female Ents) were lost. The Ents are akin to
Huorns, whom Treebeard describes as a transitional form of trees which become animated or, conversely, as Ents who grow more "treelike" over time.[sup]
[1][/sup]
Inspired by Tolkien and similar traditions, animated or
anthropomorphic tree creatures appear in a variety of media and works of fantasy.