A witch is a being with magical abilities. They are creatures that live in multiple worlds. In Lyra's world, they are always female, but there are male witches in other worlds. They can fly on cloud pine branches and have the ability to travel much farther from their dæmon than a normal human, as well as living much longer. They can also become "invisible" (very difficult to notice) by entering an acquired state of mind and can cast spells by using chants and rituals; for example, they controlled the weather to speed Lee Scoresby's hot air balloon on its way at one point. They are normally capable of healing with their spells, but the wound inflicted on Will Parry by the Subtle Knife resisted this. Their ability to separate from their dæmons is not inherent, but rather the result of their coming-of-age ritual, wherein they travel to a barren land in the North where dæmons cannot go, much like the Land of the Dead.

Witches naturally age much, much slower than humans and can live to be at least a thousand years old; Serafina Pekkala was about 300 years old and appeared to be younger than Mrs. Coulter. Witches do not suffer from human diseases, but are susceptible to other illnesses that don't affect humans. They are aware of the cold, but it is never unpleasant to them and cannot harm them, enabling them to live in the frozen North while wearing only light dresses of black silk. Witches' dæmons are always birds, presumably so that they can fly together.

Witches often had consorts to help them, such as Dr. Lanselius. They took human husbands, such as Farder Coram, but, as witches don't look like they age, their relationship never lasts. Many witches can become 1000 years of age or more. Witches are known to be very vindictive to one who turns down their love, such as Juta Kamainen with John Parry.If a witch has a child, if it is female, it will be a witch, if it is male it will be born human. Notable witches: Serafina Pekkala, Juta Kamainen, Ruta Skadi