The Drina (Serbian Cyrillic: Дрина, pronounced [drǐːna]) is a 346 km (215 mi) long international river, which forms a large portion of the border between Bosnia and Herzegovina and Serbia. It is the longest tributary of the Sava River and the longest karst river in the Dinaric Alps which belongs to the Danube river watershed. Its name is derived from the Latin name of the river (Latin: Drinus) which in turn is derived from Greek (Ancient Greek: Dreinos).