The Eastern Frontal Fault System (Spanish: Sistema de Fallas de la Falla Frontal de la Cordillera Oriental) is a megaregional system of oblique and thrust faults cross-cutting Colombia from Ecuador in the south to Venezuela in the north. The system from south to north covers ten out of 32 departments of Colombia; Nariño, Putumayo, Cauca, Huila, Caquetá, Cundinamarca, Meta, Boyacá, Casanare and Arauca. The Eastern Frontal Fault System underlies and affects the capitals of Putumayo, Mocoa, Caquetá, Florencia, Meta, Villavicencio and Casanare, Yopal. The fault system has a total length of 921.4 kilometres (572.5 mi) with a cumulative length of the faults of 1,821.8 kilometres (1,132.0 mi) and runs along an average northeast to southwest strike of 042.1 ± 19 bordering and crossing the Eastern Ranges of the Colombian Andes. The fault system forms the boundary between the North Andes microplate and the South American Plate.
Several segments of the fault system are active, with major earthquakes occurring in historical times. The 1827 Timaná (Mw 7.7), 1834 Sibundoy (Mw 7.0), 1917 Sumapaz (Mw 7.3), 1967 Neiva (Mw 7.2), 1995 Tauramena (Mw 6.5) and 2008 El Calvario earthquakes (Mw 5.6) are associated with movement of the fault system.