Derealization (DR) is a change in the way someone views the world so that it seems unreal. Derealization can also make someone feel as if their environment does not have emotion or depth. This is a symptom of other problems, such as sleeping disorders, schizophrenia, and other mental disorders. It can also be caused by drug intoxication.

Similar to derealization is depersonalization, but the two are different. Depersonalization is a sense of unreality about oneself. Derealization is a sense of unreality of the outside world.