The Cauca-Almaguer Fault is a major right-lateral fault forming the westernmost strand of Colombia's Romeral Fault System, running north to south along the Cauca River valley between the Western and Central cordilleras. It extends for several hundred kilometres through the departments of Cauca, Valle del Cauca and beyond.
The Romeral system, of which this fault is a key element, marks an ancient suture between oceanic and continental terranes and today absorbs part of the oblique convergence of the Nazca Plate against South America. The Cauca-Almaguer strand slides at a few millimetres per year and controls the linear course of the Cauca River across much of its length.
The fault has been linked to damaging historical earthquakes in southwestern Colombia and lies close to the seismically active region around Popayán, which suffered a deadly quake in 1983. As part of the broader Romeral system it is regarded as one of the principal seismic sources of the Colombian Andes.