Business process modeling is the process of mapping segments of human-perceived reality and relating these segments to one another. The choice of a modeling language determines which concepts can be used to make these descriptions, i.e., what can be mapped. Modeling languages therefore provide the vocabulary and grammar needed to represent real-life situations in models. Following the history of modeling languages for business processes, this chapter provides an overview of the basic concepts and the application of various languages such as flowcharts, event-driven process chains, activity diagrams, BPMN, and PASS (S-BPM). It concludes with a comparison of the expressive power of these languages and a guide to an informed selection of a suitable language for a given application.