Ariadne Cave System, Natural cave system in Esztergom, Hungary.

The Ariadne Cave System is a 19,300 m long cave network with a vertical extent of 206 m (139 m deep, 67 m high) in the Csévi-szirte cliffs of the Pilis hill, near Klastrompuszta. It has nine entrances, the best known being those of the Leány and Legény caves, reached by a marked trail. It was formed by gradual connection of eight caves, including the Ariadne, Rejtekút, Vacska, Indikációs, Gyökeres and Kőoszlopos caves.

The eight caves of the Csévi-szirtek were linked step by step into one system, and the Ariadne Cave Research Association has explored it since the 1990s. Its 1998 report records mapping 600 m of the Leány–Legény system and about 20 m of new passage. Since 17 May 2001 the Leány-Legény cave system has been strictly protected under ministerial decree 13/2001.

The cave system is researched by the Ariadne Karst and Cave Research Association, which has mapped sections and measured connections between entrances. Its name comes from the Ariadne Cave, one of the eight caves joined into the system. The best-known entrances, Leány and Legény caves, are reached by a marked hiking trail.

The nine entrances lie on the Csévi-szirtek cliffs near Klastrompuszta, outside Pilisszentlélek in the Pilis range, within Duna–Ipoly National Park. The best-known, the Leány and Legény entrances, are reached by a marked hiking trail. Entry requires permission from the national park directorate, and the Ariadne Karst and Cave Research Association carries out the exploration.

The system's nine entrances include the Leány and Legény caves, reachable by a marked hiking trail on the Csévi-szirtek cliffs. Researchers proved the connection between separate caves by releasing a harmless tracer gas into the Ajándék Cave in summer and detecting it at lower entrances, first in the Indikációs Cave, then in the Leány Cave.