Geopolitics (from Greek γῆ gê "earth, land" and πολιτική politikḗ "politics") is the study of the effects of Earth's geography (human and physical) on politics and international relations. While geopolitics usually refers to countries and relations between them, it may also focus on two other kinds of states: de facto independent states with limited international recognition and relations between sub-national geopolitical entities, such as the federated states that make up a federation, confederation, or a quasi-federal system.

At the level of international relations, geopolitics is a method of studying foreign policy to understand, explain, and predict international political behavior through geographical variables. These include area studies, climate, topography, demography, natural resources, and applied science of the region being evaluated.

Geopolitics focuses on political power linked to geographic space, in particular, territorial waters and land territory in correlation with diplomatic history. Topics of geopolitics include relations between the interests of international political actors focused within an area, a space, or a geographical element, relations which create a geopolitical system. Critical geopolitics deconstructs classical geopolitical theories, by showing their political/ideological functions for great powers. There are some works that discuss the geopolitics of renewable energy.

According to Christopher Gogwilt and other researchers, the term is currently being used to describe a broad spectrum of concepts, in a general sense used as "a synonym for international political relations", but more specifically "to imply the global structure of such relations"; this usage builds on an "early-twentieth-century term for a pseudoscience of political geography" and other pseudoscientific theories of historical and geographic determinism.