The movement of an organism toward or away from a supply of air. Aerotropism is the growth of a plant in the direction of an air supply, such as an air bubble in a bacterial culture chamber.

Aerotropsim applies to either a positive reaction, or towards air, or a negative reaction, which is away from air.

Aerotropism can also be the reaction to gases, generally to oxygen, particularly the growth curvature of roots or other parts of plants to changes in oxygen tension.