"Now of old the name of that forest was Greenwood the Great, and its wide halls and aisles were the haunt of many beasts and of birds of bright song; and there was the realm of King Thranduil under the oak and the beech. But after many years, when well nigh a third of that age of the world had passed, a darkness crept slowly through the wood from the southward, and fear walked there in shadowy glades; fell beasts came hunting, and cruel and evil creatures laid there their snares. Then the name of the forest was changed and Mirkwood it was called, for the nightshade lay deep there, and few dared to pass through, save only in the north where Thranduil's people still held the evil at bay. "
Mirkwood was a great forest in Middle-earth in the eastern region of Rhovanion between the Grey Mountains and Gondor.
It was also known as Greenwood the Great, Eryn Galen or Taur-e-Ndaedelos, and was later re-named Eryn Lasgalen,the Wood of Greenleaves. With the growing influence from Sauron's presence in Dol Guldur, the forest became sick and unsafe and home to more unsavory creatures, such as giant spiders. After the War of the Ring, the forest was once again returned to its days of beauty and tranquility. The Wood-elves made their home within this great forest.