Intergalactic dust is cosmic dust in between galaxies and intergalactic space. Evidence for the existence of intergalactic dust was proposed as early as 1949, and research on it grew rapidly in the late 20th century. The distribution of intergalactic dust varies greatly, and this dust may affect intergalactic distance measurements, such as to supernovae and quasars in other galaxies.
Intergalactic dust can be part of intergalactic dust clouds, which have been discovered in some other galaxies since the 1960s. By the 1980s, at least four intergalactic dust clouds have been found to exist within several megaparsecs of the Milky Way galaxy. One example is the Okroy cloud.