The Guadyerbas is a river of Spain located in the centre of the Iberian Peninsula.

It has its source in the western reaches of the Sierra de San Vicente [es],[2] at the feet of the Pico Cruces, at roughly 1,200 m above sea level.

[3] Featuring a total length of 45 km,[4] it flows westwards through the northwest of the province of Toledo, emptying in the Tiétar a few kilometres upstream from the Rosarito Reservoir [es],[5] in Oropesa.

Its waters are retained by the Navalcán Reservoir.

[1] The toponym is formed by the Arabic wadi (river) and the Spanish hierba/yerba (grass).