Perturbation or perturb may refer to:
- Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly
- Perturbation (geology), changes in the nature of alluvial deposits over time
- Perturbation (astronomy), alterations to an object's orbit—e.g., caused by gravitational interactions with other bodies
- Perturbation theory (quantum mechanics), a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one
- Perturbation (biology), an alteration of the function of a biological system, induced by external or internal mechanisms
- Perturbation (transport), operation of a transport system outside of timetable such that delays in arrival and departure from defined locations are present.
- Perturbation function, mathematical function which relates the primal and dual problems.