The Bug River (Ukrainian: Західний Буг, Zakhidnyy Buh or Western Bug; Belarusian: Захо́дні Буг, Zakhodni Buh; Russian: Западный Буг, Zapadnyy Bug) is a left tributary of the Narew river which flows from central Ukraine to the west, passing along the Ukraine-Polish and Polish-Belarusian border and into Poland, where it empties into the Narew river near Serock. The part between the lake and the Vistula River is sometimes referred to as Bugo-Narew. The Vistula River drains into the Baltic Sea.