<p>The aim of this article is to develop an approach to the unit of selection concept that fits the theory of evolution by natural selection without reproduction. I review the history of the concept to show that predominant approaches, which have recently been categorized by Suárez and Lloyd using the labels “unitary project” and “disambiguating project,” cannot be used in the context of evolution by natural selection without reproduction. I therefore propose a new and more inclusive understanding of the unit of selection that upholds the unitary project’s central claim that the concept has a unitary extension. I define the unit of selection as an entity whose interactions with the environment influence the ratio of units with similar traits in the population. That is, a unit of selection is a fitness bearer, where fitness is defined in terms that correspond to its operationalization in population genetics (without reference to heritability). This revamped unitary concept covers cases in which fitness can be reduced to reproductive output, but also cases where differential persistence or reconstitution are more important than reproduction.</p>