In population genetics, a Wright-Fisher population is a population of finite size, where each individual contributes an infinite number of gametes to a gamete pool, and then each member of the next (finite) generation is drawn from that gamete pool. This idealized population, which is the foundation of much population genetic theory, has the nice property that sampling effects can only occur at one stage (the creating of new individuals), but not at a second (the creation of the gamete pool.) To use these models for real population, we have to use the effective population size.

This model is named for R.A. Fisher and Sewall Wright, two of the founders of population genetics, who both put forward this idea.