According to superstition, witches transform themselves into black cats to avoid being seen. This image comes from European folklore linking cats with witchcraft, nighttime activity, and supernatural shape-shifting.
Black cats became especially associated with witches during early modern European witch-hunt culture. Folklore sometimes described a witch’s familiar as an animal helper, while other stories claimed that the witch herself could assume animal form. Scottish traditions also include the cat-sìth, a legendary cat-like spirit sometimes described as a witch able to transform into a cat.
The superstition is not universal. In parts of Britain, Ireland, Scotland, Japan, and Latvia, black cats have traditionally been viewed as lucky or prosperous rather than dangerous. The modern Halloween connection mainly reflects later popular culture, which combined witches, pointed hats, broomsticks, and black cats into a familiar visual tradition.
A common mix-up is assuming that every folklore tradition specifies a black cat. Some stories simply mention a cat or another animal, but the black cat is the canonical answer in the Halloween superstition commonly used in trivia.