The pair were swinging over Sulak Canyon in Dagestan when a cable holding the chair snapped.
Luckily, the girls landed on a narrow platform under the edge of the cliff, saving them from certain death.
Apart from shock, the young Russians suffered a few cuts and bruises.
Police have launched an investigation and safety checks are being carried out on similar swings nearby, where the canyon is more than one mile deep.
“The girls got scared and sustained scratches, but neither of them suffered serious injuries,” a source told Komsomolskaya Pravda.
“It is chilling to imagine what could have happened if they slipped when the swings were at a maximum height,” warned the newspaper.
The local Kazbekovsky council is now demanding all swings near the edge of the cliff be removed, said reports.
The Sulak gorge is deeper than the Grand Canyon in the US and is described as the deepest canyon in Europe.
The Ministry of Tourism in Dagestan said the swing “did not meet safety standards”.