The term climax community is an outdated ecological term for a community of plants and animals which is the result of succession, where a biological system, a community, or a soil has reached a steady state. The idea of a single climatic climax originates with Frederic Clements ' idea of the ecological community as an organic superorganism in which the various stages of successional development could be seen as analogous with the ontological development of an organism. Clement's "monoclimax" theory was contrasted with Arthur Tansley's idea of the "polyclimax" which allowed for multiple steady-state end-points in a given climatic zone. Henry Gleason 's opposition to climax theory saw him forced to the sidelines of the field of ecology. Terms such as pre-climax, post-climax, plagioclimax and disclimax were coined to account for the fact that many communities existed in states that diverged from what was expected to occur on the basis of climate.

Later developments in the field of ecology saw the decline of climax theory; theories which took into account the fact that the timelines required for the development of climax vegetation were unrealistically long, and most vegetation could better be explained by more stochastic factors. Whittaker's work undermined the superorganism idea since it could be shown that plant species distributed themselves along nutrient and other environmental gradients. In addition, the maturation of evolutionary theory discredited the level of interspecies "altruism" required by Clements' theories. More recently, palynological studies have shown that modern species assemblages are ephemeral entities - vegetation in eastern North America since the last glacial maximum has consisted of several different species assemblages, many of which have no analogies in modern "climax" communities.

Despite the fact that it is based on disproven assumptions, many authors continue to use the term climax in a diluted form to refer to what might otherwise be called mature or old-growth communities.

See also ecosystem.