In ecology, a biogeochemical cycle is a circuit or pathway by which a chemical element moves through both biotic ("bio-") and abiotic ("geo-") compartments of an ecosystem. In effect, the element is recycled, although in some such cycles there may be places (called "sinks") where the element is accumulated or held for a long period of time. The water cycle involves not a chemical element, but a molecule of great significance to life.

Biogeochemical cycles always involve equilibrium states: a balance in the cycling of the element between compartments. However, overall balance may involve compartments distributed on a global scale.

Biogeochemical cycles of particular interest in ecology are:

• nitrogen cycle
• oxygen cycle
• carbon cycle
• phosphorus cycle
• sulfur cycle
• water cycle
• hydrogen cycle