This article presents a rationale for making idioms and their use a mainstay of the second language (L2) curriculum. First, it offers a definition of the elusive term "idiom" as a point of departure for the ensuing discussion. Second, it offers five specific reasons why idiom instruction should be integrated into the L2 curriculum: here, it is argued that students' knowledge of idioms needs to be anchored in language materials and situations that are both authentic and purposeful. It is further argued that requiring students to produce idioms in ways that native speakers use them enhances students' mastery of them, facilitating the binding and mapping processes of idiom internalization. Finally, this article challenges the SLA profession to propose a systematic, theoretically informed program for developing idiomatic competence in L2 learners that is based on meaningful, authentic idiom use in the classroom and beyond.