Geographical segregation exists whenever the proportions of population rates of two or more populations are not homogenous throughout a defined space. Populations can be considered any plant or animal species, human genders, followers of a certain religion, people of different nationalities, ethnic groups, etc.

In social geography segregation of ethnic groups, social classes and genders is often measured by the calculation of indices such as the index of dissimilarity. Different dimensions of segregation (or its contrary) are recognised: exposure, evenness, clustering, concentration, centralisation, etc. More recent studies also highlight new local indices of segregation.

Geographical segregation is most often measured with individuals' place of residence, but increasing geographical data availability makes it now possible to compute segregation indexes using individuals' activity space, in whole or in part.