Germanisation, or Germanization, is the spread of the German language, people and culture. It was a central idea of German conservative thought in the 19th and the 20th centuries, when conservatism and ethnic nationalism went hand in hand. In linguistics, Germanisation of non-German languages also occurs when they adopt many German words.

Under the policies of states such as the Teutonic Order, Austria, the Kingdom of Prussia, and the German Empire, non-German minorities were often discouraged or even prohibited from using their native language, and had their traditions and culture suppressed in the name of linguistic imperialism. In addition, the Government also encouraged immigration from the Germanosphere to further upset the linguistic balance, but with varying degrees of success. In Nazi Germany, linguistic Germanisation was replaced by a policy of genocide against certain ethnic groups, even when they were already German-speaking.