In all investigative and inquiry contexts, interviews with victims, witnesses, complainants, whistleblowers and subjects or suspects, will be a key investigative strategy. However, the concept of investigative interviewing is poorly understood, and its value as an investigative strategy is undervalued, underestimated and often poorly applied. This chapter defines investigative interviewing and associated terms. It discusses it evolution to the science-based approach it is today. The key literature underpinning this evidence-based approach to information gathering is presented. Challenges involved in conducting interviews with victims, witnesses and suspects are discussed.