The Battle of the River Bug, sometimes known as the Battle of Volhynia, was a battle that took place on 22–23 July 1018, in Red Ruthenia, near the Bug River and near Volhynia (Wołyń), between the forces of Bolesław I the Brave of Poland and Yaroslav the Wise of Kievan Rus, during the Bolesław's Kiev Expedition. Yaroslav was defeated by the Polish duke. It was part of the war of succession following the death of Vladimir the Great in 1015. Boleslaw supported his son-in-law, Sviatopolk (known as Sviatopolk the Damned for his murder of his half-brothers Boris and Gleb), who was eventually defeated by Yaroslav.