In economics, Kondratiev waves (also called supercycles, great surges, long waves, K-waves or the long economic cycle) are hypothesized cycle-like phenomena in the modern world economy. The phenomenon is closely connected with the technology life cycle.

It is stated that the period of a wave ranges from forty to sixty years, the cycles consist of alternating intervals of high sectoral growth and intervals of relatively slow growth.

Long wave theory is not accepted by most academic economists. Among economists who accept it, there is a lack of agreement about both the cause of the waves and the start and end years of particular waves. Among critics of the theory, the consensus is that it involves recognizing patterns that may not exist (apophenia).