Maritsa or Maritza ( ), also known as Meriç ( ) and Evros ( ), is a river that runs through the Balkans in Southeast Europe. With a length of , it is the longest river that runs solely in the interior of the Balkan peninsula, and one of the largest in Europe by discharge. It flows through Bulgaria in its upper and middle reaches, while its lower course forms much of the border between Greece and Turkey. Its drainage area is about , of which 66.2% is in Bulgaria, 27.5% in Turkey and 6.3% in Greece. It is the main river of the historical region of Thrace, most of which lies in its drainage basin. It has its origin in the Rila Mountains in Western Bulgaria, its source being the Marichini Lakes. The Maritsa flows east-southeast between the Balkan and Rhodope Mountains, past Plovdiv and Dimitrovgrad in Bulgaria to Edirne in Turkey. East of Svilengrad, Bulgaria, the river flows eastwards, forming the border between Bulgaria (on the north bank) and Greece (on the south bank), and then between Turkey and Greece. At Edirne, the river meets it two chief tributaries Tundzha and Arda, and flows through Turkish territory on both banks. It then turns towards the south and forms the border between Greece on the west bank and Turkey on the east bank all the way to the Aegean Sea, which it enters near Enez forming a river delta. The upper Maritsa valley is a principal east–west route in Bulgaria. The unnavigable river is used for power production and irrigation. Etymology The earliest known name of the river is (, Alcman, 7th–6th century BC). Proto-Indo-European and Ancient Greek meant "wide". The Proto-Indo-European consonant cluster *-wr- shifted in Thracian to -br-, creating the Thracian name . Thereafter, the river began to be known as () in Greek and in Latin. Rather than an origin as 'wide river', an alternative hypothesis is that is borrowed from Thracian meaning 'splasher'. While the name () was used in Ancient Greek, the name () had become standard before the ancient form was artificially restituted in Modern Greek as (now: ). The name may derive from a mountain near the mouth of the river known in antiquity as or , Latinized as . History In 1371, the river was the site of the Battle of Maritsa, also known as the battle of Chernomen, an Ottoman