What is difficulty? Despite being frequently invoked in numerous normative debates, the nature of difficultyremains poorly understood. Different accounts, tailored to specific explanatory contexts, have taken hold indifferent philosophical discussions. This article shows that these accounts are too narrow to provide asatisfactory analysis of difficulty and are vulnerable to clear counterexamples. Instead, it provides analternative, empirically informed account of difficulty in terms of cognitive demand. After introducing theaccount, I show that it uniquely explains the connection between difficulty and learning. I then argue that myaccount captures the intuitions underlying existing accounts of difficulty in terms of effort, complexity, orsacrifice by showing them to be correlates of cognitive demand. I end by showcasing the broad applicabilityof this account of difficulty by looking at a set of normative debates invoking difficulty. I show thatunderstanding difficulty in terms of cognitive demand helps us make progress on pressing questions in thestudy of moral responsibility, achievement, the value of difficult action, moral demandingness, and epistemicinjustice.