Guadalajara (/ˌɡwɑːdələˈhɑːrə/ GWAH-də-lə-HAR-ə, Spanish: [ɡwaðalaˈxaɾa] ^ⓘ) is a city and municipality in Spain, located in the autonomous community of Castilla–La Mancha. It is the capital of the Province of Guadalajara.

Guadalajara lies on the central part of the Iberian Peninsula at roughly 685 meters (2,247 ft) metres above sea level. Most of the city housing is located on the left (southern) bank of the Henares, in between the river and the moors of La Alcarria. In addition to the city, the municipality also includes the villages of Iriépal, Taracena, Usanos [es], and Valdenoches [es]. As of 1 January 2025^[update], Guadalajara has a registered population of 93,470, which makes it the region's second most populated municipality.

Founded in the 9th century as Madīnat al-Faraŷ under the Emirate of Córdoba, it became a stronghold of the Masmuda Berber clan of the Banū Sālim. After Christian conquest in 1085 from the Taifa of Toledo, it grew into becoming a sizeable town of the Crown of Castile under control of the Mendoza family. It was a hub for mystical iluminismo in the 16th century in the Kingdom of Toledo. Depopulation and decay of key economy parametres ensued in the 17th century. Growth in the 21st century was caused by its closeness to the functional urban area of Madrid.

A Roman town called Arriaca, possibly founded by a pre-Roman culture, is suggested to have been located in that region. There is however no archeological proof of its existence, only references in texts such as the Ruta Antonina, which describe it as being in the hands of the Carpetani when encountered by the Romans. The city, as Caracca, was incorporated into the Roman province of Hispania Tarraconensis. The city was on the high road from Emerita (modern Mérida) to Caesaraugusta (modern Zaragoza), 22 M. P. northeast of Complutum (modern Alcalá de Henares).^{[citation needed]}

The founding of Guadalajara, dating from the Islamic period, is attributed to a person named "Faraŷ". It was officially known as Madīnat al-Faraŷ in the 9th and 10th centuries. The town was later known as Wādī Al-Ḥijāra (Arabic: وادي الحجارة), possibly meaning "Valley of Stones" (as in river gravel); in theory it may be a literal translation of the Iberian name Arriaca. It has also been proposed that Ḥajāra should not be understood as 'stones'/'gravel', but in the sense of 'castles' or 'fortified rocks'.

Wādī Al-Ḥijāra and its surroundings were part of the Middle March of Al-Andalus, controlled by the Masmuda Berber clan of the Banū Sālim who governed on behalf of the Umayyad rulers of Córdoba. During the Muslim period an alcázar (fortress) was built by the mid-9th century, as well as the Bridge over the Henares (its construction has been tentatively dated by the late 10th century or early 11th century). Walls enclosing the city were also built by then. In 920, the Banū Sālim were routed from Wādī Al-Ḥijāra (reportedly because the local population resented their rule) by Abd al-Rahman III, who attempted to directly rule the territory.

The city was part of the territory annexed by Alfonso VI of León and Castile in the 1085 conquest of the Taifa of Toledo, with Wādī Al-Ḥijāra surrendering and offering no resistance. Tradition claims however that a contingent led by Álvar Fáñez de Minaya (one of the lieutenants of El Cid) seized the city on 24 June, at night.

The area was repopulated with people from the North (Castilians from the mountains and Merindades, Basques and Navarreses mainly).^{[citation needed]}