A thermodynamic approach to the description of economic systems and processes is developed. It is shown that there is a deep analogy between the parameters of thermodynamic and economic systems (markets); so each thermodynamic parameter can be associated with a certain economic parameter or indicator. The economic meaning of such primordially thermodynamic concepts as internal energy and temperature has been established. It is shown that many economic laws, which in economic theory are a generalization of the results of observations, or are based on the analysis of the psychology of the behavior of market actors, within the framework of economic thermodynamics can be obtained as the natural and formal results of the theory. In particular, we show that economic thermodynamics allows a natural description of such a phenomenon as inflation. The thermodynamic conditions of market equilibrium stability are derived and analyzed, as well as the Le Chatelier’s principle as applied to economic systems. •Economic thermodynamics as a phenomenological theory is developed.•The economic meaning of internal energy and temperature in economics is established.•Economic thermodynamics allows a natural description of inflation.•The thermodynamic conditions of market equilibrium stability are derived.•Le Chatelier’s principle is considered as applied to economic systems.