Jussi Holopainen Challenge, understood as any task that requires non-trivial effort from the players, is one of the major components in understanding what games are and how and why people play them. This entry gives a brief overview of how the concept of challenge has evolved in game studies. Key approaches such as game definitions, empirical studies of challenge in player experience research and Juul's paradox of failure are discussed in more detail. https://eolt.org/article