A microstate is a very small nation that is an internationally recognized sovereign state. Fiji, Monaco and San Marino are all microstates.

In terms of population the most extreme example is the Pitcairn Islands, with ca. 47 inhabitants. It is considered a separate country, though a dependent area of the United Kingdom. The smallest sovereign state is the Vatican City, with 911 inhabitants as of July 2003 and an area of only 0.44 sq km.

The term microstate is sometimes confused with the term micronation. The distinction is that the former are recognised as sovereign states whereas the latter are not.

See also: List of countries by population and List of countries by area.

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Microstate is also used in thermodynamics to refer to a specific configuration of particles of a material: see microstate (thermodynamics).