Trilemma is a term in economic decision-making theory. Unlike a dilemma, which has two solutions, a trilemma offers three equal solutions to a complex problem. A trilemma suggests that countries have three options from which to choose when making fundamental decisions about managing their international monetary policy agreements. However, the options of the trilemma are conflictual because of mutual exclusivity, which makes only one option of the trilemma achievable at a given time.

Trilemma often is synonymous with the "impossible trinity," also called the Mundell-Fleming trilemma.