This is a list of the longest-living organisms that is, the individuals (in some instances, clones) of a species. This may be, for a given species
Ordinarily, this does not consider the age of the species itself, comparing species by the range of age-span of their individuals, or the time between first appearance (speciation) and extinction of the species.
If the mortality rate of a species does not increase after maturity, the species does not age and is said to be biologically immortal. Many examples exist of plants and animals for which the mortality rate actually decreases with age, for all or part of the lifecycle.
If the mortality rate remains constant, the rate determines the mean lifespan. The lifespan can be long or short, though the species technically "does not age".
Other species have been observed to regress to a larval state and regrow into adults multiple times.
As with all long-lived plant and fungal species, no individual part of a clonal colony is alive (in the sense of active metabolism) for more than a very small fraction of the life of the entire colony. Some clonal colonies may be fully connected via their root systems, while most are not actually interconnected, but are genetically identical clones which populated an area through vegetative reproduction. Ages for clonal colonies, often based on current growth rates, are estimates.
Some endoliths have extremely long lives. In August 2013, researchers reported evidence of endoliths in the ocean floor with a generation time of 10 millennia. These are slowly metabolizing, not in a dormant state.
These are single examples; for a broader view, see Life expectancy (includes humans).
Rachel Sussman (2014). The Oldest Living Things in the World. Chicago: University of Chicago Press. ISBN .