The Kazmierz Sosnowski Main Beskid Trail (Polish Gà Âówny Szlak Beskidzki imienia Kazmierza Sosnowskiego, "GSB") is a long-distance trail marked in red that leads from Ustroà  in the Silesian Beskids to Woà Âosate in the Bieszczady Mountains.
At about , it is the longest trail in the Polish mountains. It crosses the Silesian Beskid, the à »ywiec Beskid (Beskid à »ywiecki), the Gorce Mountains, Beskid Sàdecki, the Low Beskids (Beskid Niski) and the Bieszczady Mountains. Covering the highest parts of the Polish Beskids, it crosses peaks such as Stoà ¼ek Wielki (Velký Stoà ¾ek in Czech ), Barania Góra, Babia Góra, Polica, Turbacz, Lubaà Â, Przehyba, Radziejowa, Jaworzyna Krynicka, Rotunda, Cergowa, Chryszczata, Smerek and Halicz as well as towns such as Ustroà Â, WÃÂgierska Górka, Jordanów, Rabka-Zdrój, Kroà Âcienko nad Dunajcem, Rytro, Krynica-Zdrój, Iwonicz-Zdrój, Rymanów-Zdrój, Komaà Âcza, Cisna and Ustrzyki Górne.
The trail was created during the interwar period. The route of the western part (Ustroà Â-Krynica) was designed by Kazimierz Sosnowski and it was finished in 1929. The eastern was designed by Mieczysà Âaw Orà Âowicz. It was completed 1935 and it led to Chornohora which, at the time, was located within the borders of Poland. Between 1935 and 1939, the trail was named after Józef Pià Âsudski.
Many Polish ultrarunners have attempted to set new records on the trail. The current fastest known time on the trail belongs to Kamil Leà Âniak, who covered the trail in 93 hours, 42 minutes, and 22 seconds, beating the prior record by just under two minutes. This was a supported run, which means that the athlete could work with an external support team.