The Danube is the longest river in Romania. It travels about 1,075 kilometers, almost 40% of its length, through Romania. Almost all of Romania's rivers are either direct or indirect tributaries of the Danube. The most important of these rivers are the Mureş River, the Olt River, the Prut, the Siret River, the Ialomiţa River, the Someş River, and the Argeş River.