Multiobjective optimization addresses decisions involving multiple, often conflicting, goals. This chapter introduces fundamental concepts such as Pareto optimality, trade-offs between objectives, and duality for multiobjective optimization problems. The chapter then illustrates how such models reflect real-world complexity in areas such as the design of policies, where efficiency, equity, and sustainability must be balanced. In the model of the firm facing a bicriteria objective function (maximization of the profit and the revenue) it can be shown that rate of return types of regulation lead to a suboptimal use of production factors.