German has the most native speakers among the languages of the European Union.
German is a West Germanic language and the principal official language of Germany, Austria, and Liechtenstein. It is also co-official in Switzerland, Belgium, and Luxembourg. When native speakers within the European Union are compared, German has the largest total, with most of them living in Germany.
German became one of the European Union’s official languages when the European Economic Community was founded in 1958, and it remains one of the EU’s 24 official languages. The standard language is commonly called Standard German, while regional varieties include Alemannic, Bavarian, and Low German traditions.
German is sometimes confused with the most widely learned or most widely spoken EU language overall. Those rankings change when second-language speakers are included. This question uses native speakers, which is why German leads over languages such as French, Italian, and Spanish in the EU context.