Dust in Philip Pullman's trilogy of novels His Dark Materials is a fictional form of dark matter (as we call it in our world), an elementary particle that is of fundamental importance to the novels. In most universes including our own Dust is invisible to the naked eye, but can be seen once The Amber Spyglass has been invented, as well as on special film.

Unlike ordinary particles Dust is conscious. It falls from the sky and is attracted to people (especially adults) and objects made by people, which makes it of great interest to the Church which thinks that it may be the physical manifestation of Original Sin. We later learn that Dust is actually a kind of cosmic force for good, conferring consciousness, knowledge and wisdom.

It is Dust that provides the answers given by the alethiometer, and by the I Ching system of divination. Dust was previously known (in Lyra Belacqua's universe) as Rusakov particles after their discoverer, Boris Rusakov, and has other names in other worlds, including sraf (in the world of the mulefa).

Angels, including The Authority, are formed when Dust condenses, but they are not in reality the human-like figures they appear to be.

See also The Book of Dust, a forthcoming Pullman novel in the same series.