The Sierra de Ayllón (Ayllón mountain chain) or Macizo de Ayllón (Ayllón massif) is a mountain chain of the Iberian Peninsula, belonging to the Sistema Central, of which it constitutes one of its easternmost spurs. It is located between the Spanish provinces of Guadalajara, Segovia and Madrid. The mountain chain consists of a natural area protected within the Natura 2000 network as a Site of Community Importance and Special Protection Area for Birds, located in the northwest of the province of Guadalajara in the autonomous community of Castilla-La Mancha. The natural area of Ayllón occupies the Paleozoic massif of the Sierra de Ayllón, in the province of Guadalajara, including the main core whose highest peak is the Pico del Lobo (2269 m), and the Sierras de la Concha (1865 m), Pico Ocejón