In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and subsequently recovering. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities such as deforestation, fracking of the ground for oil extraction, pesticide sprayed in soil, and the introduction of exotic plant or animal species. Disturbances of sufficient magnitude or duration can profoundly affect an ecosystem and may force an ecosystem to reach a threshold beyond which a different regime of processes and structures predominates. When such thresholds are associated with a critical or bifurcation point, these regime shifts may also be referred to as critical transitions.

Human activities that adversely affect ecological resilience such as reduction of biodiversity, exploitation of natural resources, pollution, land use, and anthropogenic climate change are increasingly causing regime shifts in ecosystems, often to less desirable and degraded conditions. Interdisciplinary discourse on resilience now includes consideration of the interactions of humans and ecosystems via socio-ecological systems, and the need for shift from the maximum sustainable yield paradigm to environmental resource management and ecosystem management, which aim to build ecological resilience through "resilience analysis, adaptive resource management, and adaptive governance". Ecological resilience has inspired other fields and continues to challenge the way they interpret resilience, e.g. supply chain resilience.

The IPCC Sixth Assessment Report defines resilience as, “not just the ability to maintain essential function, identity and structure, but also the capacity for transformation.” The IPCC considers resilience both in terms of ecosystem recovery as well as the recovery and adaptation of human societies to natural disasters.

The concept of resilience in ecological systems was first introduced by the Canadian ecologist C.S. Holling in order to describe the persistence of natural systems in the face of changes in ecosystem variables due to natural or anthropogenic causes. Resilience has been defined in two ways in ecological literature:

The second definition has been termed ‘ecological resilience’, and it presumes the existence of multiple stable states or regimes.

For example, some shallow temperate lakes can exist within either clear water regime, which provides many ecosystem services, or a turbid water regime, which provides reduced ecosystem services and can produce toxic algae blooms. The regime or state is dependent upon lake phosphorus cycles, and either regime can be resilient dependent upon the lake's ecology and management.

Likewise, Mulga woodlands of Australia can exist in a grass-rich regime that supports sheep herding, or a shrub-dominated regime of no value for sheep grazing. Regime shifts are driven by the interaction of fire, herbivory, and variable rainfall. Either state can be resilient dependent upon management.

Ecologists Brian Walker, C S Holling and others describe four critical aspects of resilience: latitude, resistance, precariousness, and panarchy.