This chapter outlines the Intervention Mapping (IM) approach, a planning framework for the systematic development, implementation, and evaluation of health promotion interventions. IM is a comprehensive approach to intervention development in general. This chapter describes the six steps of IM and emphasizes using it for digitally supported interventions within the context of public health specifically. The chapter starts by describing Core Processes, a systematic way of answering planning questions to safeguard the use of available evidence and insights from theory. Subsequently, this chapter zooms in on understanding behavior as this is key during the development of health-promoting interventions that aim to establish behavior change. Successively, the steps of IM are discussed separately and illustrated by examples of interventions that use digital technology in the context of public health. This chapter guides readers through the six IM steps and hopes to inspire them to learn more about IM and behavior change principles and their use for digital interventions.