In the 1950’s, W. Ross Ashby introduced the Law of Requisite Variety in the context of General Systems Theory. A key concept underlying this theory is the notion of variety, defined as the total number of distinct states of a system (in the most general sense). We argue that domain modelling (including enterprise modelling) needs to confront different forms of variety, also resulting in a need to “reflect”/“manage” this variety. The aim of this paper is to, inspired by Ashby’s Law of Requisite Variety, explore some of the forms of variety that confront domain modelling, as well as the potential consequences for models, modelling languages, and the act of modelling. To this end, we start with a review of our current understanding of domain modelling (including enterprise modelling), and the role of modelling languages. We then briefly discuss then notion of Requisite Variety as introduced by Ashby, which we then explore in the context of domain modelling.