Frankfurt an der Oder is a town in Brandenburg, Germany, located on the Oder River, on the German-Polish border directly opposite the town of Słubice, which was part of Frankfurt until 1945. At the end of the 1980s, it reached a population peak with more than 87,000 inhabitants.

The official name Frankfurt (Oder) and the older Frankfurt an der Oder are used to distinguish it from the larger city of Frankfurt am Main.

The town of Frankfurt received its charter in 1253 at the Brandendamm, although the settlement is probably considerably older. The early settlers lived on the western banks of the Oder; later the town was extended to the eastern bank (today's Słubice). In late medieval times, the town dominated the river trade between Breslau (Wrocław) and Stettin (Szczecin). In 1430, Frankfurt joined the Hanseatic League, but was a member for only a short time.

In April 1631, during the Thirty Years' War, Frankfurt was the site of the Battle of Frankfurt an der Oder between the Swedish Empire and the Holy Roman Empire. After a two-day siege, Swedish forces, supported by Scottish auxiliaries, stormed the town. The result was a Swedish victory.

The city was briefly occupied by the Russian Imperial Army during the Seven Years' War, in August 1759, in the prelude to the battle of Kunersdorf.

With the dissolution of the Margraviate of Brandenburg during the Napoleonic Wars, Frankfurt became part of the Province of Brandenburg in 1815. In the 19th century, Frankfurt played an important role in trade. Centrally positioned in the Kingdom of Prussia between Berlin and Posen (Poznań), on the river Oder with its heavy traffic, the town housed the second-largest annual trade fair (Messe) of the German Reich, surpassed only by that in Leipzig.

There was no fighting for the town in 1945 during World War II even though the town was declared a fortress (Festung) in an attempt to block the Red Army's route to Berlin. The nearly empty town was burned down. The postwar German-Polish border ran along the Oder, separating the Dammvorstadt on the eastern bank - which became the Polish town of Słubice - from the rest of Frankfurt. While part of communist East Germany, Frankfurt was administered within Bezirk Frankfurt (Oder). It became part of the reconstituted state of Brandenburg with German reunification in 1990.