Ballspielverein Borussia 09 e.V. Dortmund, commonly known as Borussia Dortmund [boˈʁusi̯a ˈdoɐ̯tʰmuntʰ], Dortmund, or BVB, is a German sports club based in Dortmund, North Rhine-Westphalia. Borussia Dortmund plays in the Bundesliga, the top tier of the German football league system. Dortmund is one of the most successful clubs in German footballhistory. They are the current Bundesliga champions.

Borussia Dortmund was founded in 1909 by seventeen football players from Dortmund. Borussia Dortmund have won eight German football championships, three German Cups, four German Supercups, one UEFA Champions League, one UEFA Cup Winners' Cup, and one Intercontinental Cup. Their UEFA Cup Winners' Cup win in 1966 made them the first German club to win a European title.

Since 1974, Dortmund have played their home games at Westfalenstadion. The stadium is the biggest stadium in Germany. Borussia Dortmund's colors are black and yellow. Dortmund holds a long-standing rivalry with Schalke. Matches between the two clubs are referred to as the Revierderby. In the last two decades, a strong rivalry with Bayern Munich has emerged, known asDer Klassiker (English: The Classic). Borussia Dortmund's motto is "Echte Liebe" (English: "True Love").