Geopolitik was a German school of geopolitics which existed between the late 19th century and World War II.

It developed from the writings of various European and American philosophers, geographers and military personnel, including Oswald Spengler (1880–1936), Alexander Humboldt (1769–1859), Karl Ritter (1779–1859), Friedrich Ratzel (1844–1904), Rudolf Kjellén (1864–1922), Alfred Thayer Mahan (1840–1914), Homer Lea (1876–1912), Halford Mackinder (1861–1947) and Karl Haushofer (1869–1946). The ideology of Adolf Hitler adapted, and eventually incorporated some of its tenets.

The defining characteristic of Geopolitik is the inclusion of organic state theory, informed by social Darwinism. It was characterized by clash of civilizations-style theorizing. It is perhaps the closest of any school of geostrategy to a purely nationalistic conception of geostrategy, which ended up masking other more universal elements.

Germany acted as a revisionist state within the international system during both World Wars by attempting to overthrow British domination, and to counter what it saw as rising US and Russian hegemony. As a latecomer to nationhood proper, lacking colonies or reserved markets for industrial output but also experiencing rapid population growth, Germany desired a more equitable distribution of wealth and territory within the international system. Some modern scholars have begun to treat the two World Wars, participated in by Germany, as a single war (1914–1945) in which the revisionist Germany attempted to bid for hegemonic control with which to reorder the international system.

German foreign policy was largely consistent in both wars. The foreign policy of Nazi Germany (1933–1945) was unique insofar as it learned from what it saw as past imperial mistakes but essentially followed the very same designs laid out by German Geopolitik in the historical record of the German Empire.

German geopolitik contributed to Nazi foreign policy chiefly in the strategy and justifications for Lebensraum. It contributed five ideas to German foreign policy in the interwar period: the organic state; lebensraum; autarky; pan-regions and the land power/sea power dichotomy.

Geostrategy as a political science is both descriptive and analytical like political geography but adds a normative element in its strategic prescriptions for national policy. While it stems from earlier US and British geostrategy, German geopolitik adopts an essentialist outlook toward the national interest, oversimplifying issues and representing itself as a panacea. As a new and essentialist ideology, geopolitik found itself in a position to prey upon the post–World War I insecurity of the populace.

In 1919, General Karl Haushofer would become professor of geography at the University of Munich. That would serve as a platform for the spread of his geopolitical ideas, magazine articles and books. By 1924, as the leader of the German geopolitik school of thought, Haushofer would establish the Zeitschrift für Geopolitik monthly, devoted to geopolitik. His ideas would reach a wider audience with the publication of Volk ohne Raum by Hans Grimm in 1926, popularizing his concept of lebensraum. Haushofer exercised influence both through his academic teachings, urging his students to think in terms of continents and emphasizing motion in international politics, and through his political activities. While Hitler's speeches would attract the masses, Haushofer's works served to bring the remaining intellectuals into the fold.