Disambiguation: This page refers to the sub-discipline of condensed matter physics, not the branch of meteorology concerned with the study of weather systems smaller than synoptic scale systems.

Mesoscopic physics is a subdiscipline of condensed matter physics that deals with materials of an intermediate length. The scale of such materials can be described as being between the size of a quantity of atoms (such as a molecule) and of materials measuring micrometres. The lower limit can also be defined as being the size of individual atoms. At the micrometre level are bulk materials. Both mesoscopic and macroscopic objects contain a large number of atoms. Whereas average properties derived from its constituent materials describe macroscopic objects, as they usually obey the laws of classical mechanics, a mesoscopic object, by contrast, is affected by fluctuations around the average, and is subject to quantum mechanics.