Intentionalism is the least investigated approach to treaty interpretation. It is often discredited by international legal scholars on the basis of various pragmatic arguments. It is also normatively discouraged as a threat to the stability and predictability of treaty rules. At the same time, even a cursory glance at the case law of international courts and tribunals would be sufficient to realize that treaty interpretation discourse in practice is replete with references to the parties’ intention. This chapter situates the reluctance of international legal scholars about intentionalism in the broader intellectual history of international law and shows that most objections to intentionalism rest on a mentalist understanding of intention that has been severely criticized in philosophy. It also argues that given intentionalism’s close connection with consensualism, it is unrealistic to believe that it can be dismissed in practice.