The European long-distance paths (trails) are a network of long-distance footpaths that traverse Europe. The paths were designated by the European Ramblers' Association. In general the routes make use of existing national and local trails.
The Association was founded in Germany in 1969. Today, this organisation comprises more than 55 ramblers’ organisations from 30 European states. Three of international trails pass through Bulgaria - E3. E4 and E8. 
 
 
 
E 3 Trail
The E3 European long distance path, is a 6,950-kilometre (4,320 mi) long-distance footpath that is planned to run from the Portuguese coast to the Black Sea in Bulgaria. The completed sections of the route pass through Spain, France, Luxembourg, Belgium, Germany, the Czech Republic, Slovakia, Poland, Hungary, and Bulgaria.
In Bulgaria it follows the crest of Balkan Mountain (Stara Planina) – the longest mountain chain in Bulgaria. It spreads from the Belogradchik Pass to cape Emine at the Black Sea coast and covers some 10% of the total area of the country. Its average elevation is 735 m. The central section of Stara Planina is of the highest elevation – the crest often rises above 2000 m. Of all the 29 peaks with an elevation above 2000 ΠΌ 25 are located in Central Stara Planina.
The international hiking trail Kom-Emine has a length of around 700 km. The trail is marked by special signs with the initials E-3 and paint marking – white-red-white marks. At many sites the paint marking coincides with the winter one (pillars with yellow-black-yellow color) and the crest of Balkan Mountain.    More details
 
E 4 TRAIL
 E 4 Trail

The E4 European long distance path starting in Spain at its westernmost point and leading through France, Switzerland, Germany, Austria, Hungary, Romania and Bulgaria to end in Greece. It visits the Greek island of Crete as well as Cyprus.
In Bulgaria the trail E4 begins on the village square of the Sofia suburb of Dragalevtsi. It passes the terminals of the Dragalevtsi chairlift and the highest peak of the Vitosha mountains, Cherni Vrah, and then leads down the other side of Vitosha, through the Verila hills to Rila mountain.
In the Rila and Pirin Mountains, the main trail leading through those mountains, marked in red, should be followed. Coming from Verila, the trail enters Rila. It passes through the Seven Rila Lakes area and then climbs onto the ridge passing Malyovitsa peak. It continues via the shelter Kobilino Branishte, the hut at Ribni Ezera and the hut Macedonia towards the Predel saddle which separates Rila from Pirin.
From Predela, it reaches the main ridge of Pirin via the hut Yavorov and follows it via the three highest peaks of Pirin (Banski Suhodol, Kutelo and Vihren) and the ridge Koncheto, before descending to the Vihren refuge. It continues on the ridge until the Vinarska Porta saddle, and then runs along Tevno Lake and down the Zhelezina stream towards Pirin hut. From there it is the only marked trail leading through the Central Pirin range, passing the peak Orelyak and the hut Popovi Livadi. It ends at Petrovo near the Greek border, where a bus to Kulata on the border can be taken. Total length within Bulgaria is 250 km.

E 8 TRAIL

E 8 TrailThe E8 European long distance path leading 4,700 km (2,920 miles) across Europe, from Cork in Ireland to Istanbul in Turkey. After Ireland it crosses the Irish Sea into the United Kingdom, where it follows part of the Trans Pennine Trail. After crossing the North Sea, it passes through the Netherlands, Germany, Austria, Slovakia, Poland, Ukraine and Romania. It finally crosses Bulgaria before reaching Turkey.