A trophic cascade is a powerful indirect interaction that can control entire ecosystems. It occurs when a trophic level in a food web is suppressed, and the impact of a predator on its preys ecology trickles down one more feeding level to affect the density and/or behavior of the preys prey, which ecologists term this interaction a feeding, or trophic cascade. Trophic cascades by definition must occur across a minimum of three feeding levels. There are two types of trophic cascades: top-down and bottom-up. A top-down cascade is a trophic cascade where the top consumer/predator controls the primary consumer population.

Trophic cascades were originally thought to be rare, but now we understand that they occur across diverse terrestrial, freshwater, and marine ecosystems, and are common features of many green plant communities. The earliest documented trophic cascades all occurred in lakes and streams, leading a scientist to speculate that fundamental differences between aquatic and terrestrial food webs made trophic cascades primarily an aquatic phenomenon. However, subsequent research has documented trophic cascades in terrestrial ecosystems as well.

Trophic cascades can be important for understanding the knock-on effects of removing top predators from food webs, as humans have done in many places through hunting and fishing. They are powerful interactions that strongly regulate biodiversity and ecosystem function.