21st Vistula Uhlan Regiment (Polish: 21 Pułk Ułanów Nadwiślańskich, 21 puł) was a cavalry unit of the Polish Army in the Second Polish Republic. Formed in 1920, it fought both in the Polish–Soviet War and the Invasion of Poland. The regiment was garrisoned in the town of Rowne, Volhynia, and in 1939 belonged to Volhynian Cavalry Brigade.