In Macbeth, Birnam Wood is the forest that surrounds Macbeth's castle. It is important because it is where Macbeth first sees the witches' prophesy come true. In Act IV, Scene 1, Macbeth sees a woodcutter carrying branches from the forest and realizes that the witches' prophecy is coming true: Birnam Wood shall come to Dunsinane. This event foreshadows his defeat and death.