Policy congruence is concerned with the similarity of policy preferences of voters on the one hand and the preferences and actions of representatives on the other hand. This chapter outlines the great diversity in the way policy congruence is studied, in terms of who the representatives are, whether congruence measured on a single ideological dimension, for specific issues or as issue priority, and whether one looks at the entire distribution of preferences of both represented and representatives or reduces them to a single position for each side, such as the median. Explanations of policy congruence have mostly focused on electoral systems. Findings are mixed, with proportional systems generally somewhat stronger in terms of congruence between voters and legislatures, and plurality systems providing a stronger link between legislatures and government’s policies. More recent work focuses on inequalities in policy congruence and the consequences of policy congruence for satisfaction with democracy.