Margrave Otto V of Brandenburg-Salzwedel (c. 1246 – 1298), nicknamed Otto the Tall, was a son of Margrave Otto III and co-ruler of Brandenburg with his cousin, Margrave Otto IV.
Otto V spent many years in Prague, at the court of his maternal uncle King Ottokar II of Bohemia. When Ottokar died in battle in 1278, Otto V became the regent for Ottokar's son and heir Wenceslaus II, who was only seven years old when his father died. As regent, Otto V had to deal with the machinations of Ottokar's widow Kunigunda of Slavonia and with factions of powerful noblemen. Bohemian chroniclers describe Otto's persistent rigour and that Wenceslaus was forced to give up his claims on Upper Lusatia before he could start reigning himself. When Wenceslaus had taken over, he and Otto V were still on good terms, and Wenceslaus took measures against the strong influence of the group around his mother.
Otto V also persistently defended his claims on Pomerania against Polish counter-claims.