Medinaceli (pronounced [meðinaˈθeli]) is a municipality and town in the province of Soria, in Castile and León, Spain. Built on a hilltop at about 1210 metres above sea level, the town oversees the Jalón valley. The municipality includes other villages like Torralba del Moral. The A-15 and A-2 motorways link up in the municipality.

Its name derives from the Masmuda tribe مدينة سليم madīnat salīm, which was named after the berber Tribe of Masmuda.

Situated at the confluence of the rivers Jalón and Arbujuelo, Medinaceli was the site of the Celtiberian town known as Occilis or Okilis.

During the Islamic period it enjoyed the status of madina (city). In this period, the Berber Banū Salīm, a lineage of the Masmuda tribal group, installed in the area. Even after the Banū Salīm fell from grace and were routed in 920, Medinaceli retained its strategic importance for Cordobese authorities, serving as a powerbase for military operations in the north, including the campaign against Christian settlements in the upper Duero and the curbing of the Banu Tujib revolt. Medinaceli became the head of the Middle March in 946.

Built between the 1st and 3rd centuries CE, Medinaceli is home to the only three-gated Roman arch in Spain. The arch is used as Spain Historic site symbol throughout the country.

The castle of Medinaceli served as the residence of the Dukes of Medinaceli until the Ducal Palace (Palacio Ducal) was used for this purpose.

Other buildings include the Colegiata de Nuestra Señora de la Asunción, whose abbots fought with the bishops of Sigüenza to maintain the city's rights. The Convent of Saint Elizabeth (16th century) (Convento de Santa Isabel), which lies next to the church of San Martín, also stands in good condition. The beaterio (house inhabited by lay sisters) of San Román (Saint Romanus) is in ruins; it may have previously been a synagogue.

Moorish-era remains include a stone gate, one of the few remains of the ancient city walls.