In this chapter, we identify the strongest measures of forgiveness, describe their psychometric properties, and outline a research agenda to strengthen the measurement of forgiveness. Results of a systematic literature search included measures of forgiveness of others at the offense, relationship, and trait levels; forgiveness of self at the offense and trait levels; and forgiveness of groups at the offense and relationship levels. We discuss in greater detail recent innovations in the measurement of forgiveness including relationship-specific forgiveness of others, factors influencing the forgiveness process, and intergroup forgiveness. Although the measurement of forgiveness has made steady progress, issues of mono-method bias, social desirability bias, and lack of longitudinal studies still plague the forgiveness literature. We outline several ways to address these concerns.