The Wicked Witch of the West, also known as just the Wicked Witch, is a fictional character from L. Frank Baum's children's book The Wonderful Wizard of Oz.

In the book, the Wicked Witch is the one witch of Oz that the Wizard of Oz is afraid of. She rules the Winkie Country in the western part of Oz, and the Wizard makes his help for Dorothy (who killed the Wicked Witch of the East, the only other wicked witch in Oz), the brainless Scarecrow, the heartless Tin Woodman, and the Cowardly Lion, conditional on their killing the Wicked Witch. The four journey toward her castle and are attacked by wolves, crows, bees, and her Winkie slaves. Dorothy and her companions defeat each threat, but are subdued by the Winged Monkeys that the Wicked Witch commands through the power of the Golden Cap. Dorothy and the Cowardly Lion are carried to the Wicked Witch's castle, where she is made to wait on her. The Wicked Witch can't kill Dorothy because she's protected by the Good Witch of the North, so she tricks her into tripping over an iron bar to get one of her magic Silver Shoes. In anger, Dorothy throws a bucket of water onto the Wicked Witch and causes her to melt away.

W.W. Denslow's illustrations for The Wonderful Wizard of Oz depict the Wicked Witch as a paunched old woman wearing an eyepatch; her good eye gave her the visual acuity of a telescope. In the 1939 movie The Wizard of Oz, the Wicked Witch played by Margaret Hamilton was tall, green-skinned, and dressed entirely in black. It is from this witch popular culture gets the oft-quoted mocking, "I'll get you, my pretty, and your little dog too!" followed by a maniacal laugh. (The song lyrics, "Ding Dong, The Witch is Dead", come not from her death, but the death of her sister, the Wicked Witch of the East.)

A modern story told from the point of view of Elphaba, the child who grows up to become the Wicked Witch, is available as Wicked - The Life and Times of the Wicked Witch of the West by author Gregory Maguire. Maguire's story was developed into a Broadway musical, Wicked, in 2003. Idina Menzel won the 2004 Tony Award for Best Performance by a Leading Actress in a Musical for her portrayal of Elphaba.