Vom Kriege (German pronunciation: [fɔm ˈkʁiːɡə]) is a book on war and military strategy by Prussian general Carl von Clausewitz, written mostly after the Napoleonic wars, between 1816 and 1830, and published posthumously by his wife in 1832. It has been translated into English several times as On War. On War is actually an unfinished work; Clausewitz had set about revising his accumulated manuscripts in 1827, but did not live to finish the task. His wife eventually compiled all the work and the final two chapters Clausewitz never finished.

Clausewitz integrates politics and social and economic issues as some of the most important factors in deciding the outcomes of a war. It is one of the most important treatises on strategy ever written, and is prescribed at various military academies to this day.