The flag of Brandenburg (Civil and Sate) is a horizontal bi-colour of red over white, with the arms of the state (land), in the center. The coat of arms of the state shows on a shield in white (silver) a red eagle, looking to the right, with wings decorated with trefoils in gold and armoured gold. In its current form, the flag was adopted on 20 January 1991, with further enshrinement in Article 4 of the Constitution of the State of Brandenburg.

The Margraviate of Brandenburg, also known as the March of Brandenburg, played a pivotal role in forming the nucleus of what over the course of history became the Kingdom of Prussia and the German Empire. The Märkischer Adler, or red eagle of the Margraviate of Brandenburg was adopted by Margrave Gero in the 10th century. The bi-colour of red over white was used by the Province of Brandenburg in both the Kingdom of Prussia and also in the Free State of Prussia.