Greenwood the Great becomes Mirkwood after corruption in Tolkien’s Middle-earth. The forest lies in northern Rhovanion and is one of the major settings of The Hobbit and The Lord of the Rings.
In The Hobbit, the woodland is already known as Mirkwood, and its dangers include giant spiders, hostile Elves, and the influence of the Necromancer at Dol Guldur. Tolkien’s wider history explains that the forest’s earlier name was Greenwood the Great before the shadow of Sauron spread through it.
Readers sometimes confuse Mirkwood with Fangorn Forest, which is farther west and is home to the Ent Treebeard. Lothlórien is another famous woodland realm, ruled by Galadriel and Celeborn, while Doriath belongs to the older First Age stories. These forests are distinct places from different periods of Tolkien’s legendarium.