This is a list of the longest-living biological organisms: the individuals or clones of a species with the longest natural maximum life spans. For a given species, such a designation may include:
- The oldest known individual(s) that are currently alive, with verified ages.
- Verified individual record holders, such as the longest-lived human, Jeanne Calment, or the longest-lived domestic cat, Creme Puff.
The definition of "longest-living" used in this article considers only the observed or estimated length of an individual organism's natural lifespan – that is, the duration of time between its birth or conception (or the earliest emergence of its identity as an individual organism) and its death – and does not consider other conceivable interpretations of "longest-living", such as the length of time between the earliest appearance of a species in the fossil record and the present day (the historical "age" of the species as a whole) or the time between a species' first speciation and its extinction (the phylogenetic "lifespan" of the species). This list includes long-lived organisms that are currently still alive as well as those that have already died.