Metacognition is defined as an individual’s knowledge and thoughts about their own cognitive processes. Applied to endurance activities, metacognition includes knowledge of cognitive strategies, such as relaxation or motivational self-talk, and the ability to implement these strategies in a situationally-appropriate manner. This chapter discusses the importance of metacognition to endurance activity. Relationships between metacognition and psychological states underlying excellent performance are also highlighted. Throughout, practical examples are provided to facilitate an understanding of metacognition in endurance contexts. Finally, avenues for future research are proposed, including a need to conduct more non-running orientated metacognition research, and proposals to improve measurement of metacognitive processes in endurance activities.