The availability and dissemination of information have very significant effects on individual behaviour and on the functioning of the markets. The nature of the contracts traded, the mechanisms and operating rules of the markets often reflect the prevailing information conditions. This course is an introduction to these topics through the methodologies of microeconomic theory. In particular, a first part is dedicated to decisions under uncertainty in perfectly competitive markets. A second part considers decisions with incomplete information and imperfectly competitive markets (monopoly, oligopoly, monopolistic competition); the emergence of strategic behaviours is considered. A final part of the course is dedicated to the functioning of markets in the presence of information asymmetries. Understanding these issues aims to put the student in a position to understand the information that market data transmits and to identify which other data it is important to collect in order to effectively inform the decisions of economic agents.