Kremenec, Mountain summit at the Poland–Slovakia–Ukraine tripoint, Bukovské vrchy

Krzemieniec is a mountain summit in the Bieszczady range, sitting at 1221 meters where Poland, Ukraine, and Slovakia meet at a single point. It is the only tripoint shared by these three countries, and marked trails lead to it from each side of the border.

Originally called Rouny verch, the summit was renamed Ruský kameň (Hungarian Kremeny–Orosz, 'Ruthenian Stone') after a mid-19th-century boundary dispute between Nová Sedlica and Stará Stužica. From 1918 to 1939 it marked the meeting of Czechoslovakia, Poland and Poland's southern neighbour; from 1939 to 1945 that of Hungary and the German Reich; from 1945 to 1991 Czechoslovakia, Poland and the Soviet Union; today Slovakia, Poland and Ukraine.

Locals still call the peak Kremenaroš, a name tied to the Ruthenians who settled this borderland. In the mid-19th century a court dispute between Nová Sedlica and Stará Stužica led to a new county tripoint on the summit, officially named Ruský kameň (Ruthenian Stone). The granite monument at the tripoint, installed in 2000, bears the border designations in Slovak, Polish and Ukrainian.

The summit can be reached from Poland, Ukraine, or Slovakia using marked trails, but conditions and trail upkeep vary by country and season. Near international borders, it is worth checking entry requirements for each side before setting out.

The summit lies on the Polish-Ukrainian border, while the tripoint with Slovakia sits about 170 m southwest at 1,207.7 m. The granite monument there was flown in by a Slovak Interior Ministry flight crew and set on 6 September 2000; it marks the easternmost point of Slovakia.