The Sanctuary of Our Lady of Arantzazu [aˈɾants̻as̻u] is a Franciscan sanctuary located in Oñati, Basque Country, Spain. The shrine is a much appreciated place among Gipuzkoans, with the Virgin of Arantzazu being the sanctuary's namesake and patron saint of the province along with Ignatius of Loyola.

The place benefits from the highland silence and peaceful atmosphere of the Aizkorri mountain range along with a good road infrastructure, so the place is frequently visited by devotees and regional and foreign tourists alike. It is located in the site where presumably the Virgin of Arantzazu appeared to the shepherd Rodrigo de Balanzategui in 1468. Legend has it the figure of the Virgin was in a thorn-bush, and his exclamation "Arantzan zu?!" (Thou, among the thorns?!) gave rise to the name of the place. According to the linguistic explanation, the name stems from "arantza + zu", 'place abounding in hawthorn'.

Arantzazu can be found as a female name in Spain in the forms of Arantza and Arantzazu (especially in Biscay and Gipuzkoa) along with Arancha (Spanish spelling) or Arantxa (Basque spelling), much in line with Spanish phonetics.

The place is also a starting point for several mountains trails and circuits for hikers that provide access to the meadows of Urbia and on to the mountain range Aizkorri, to the massif Aloña and to the lands south and east of the shrine. All the trails are well signalled.

Pope Leo XIII granted a Canonical coronation to the image on 6 June 1886. A variant replica bearing its same title was brought to the Philippines in 1705, featuring a standing posture. Pope Francis granted a Canonical coronation to the Philippine image on 31 May 2017. The image is currently enshrined in the Diocesan Shrine and Parish of Our Lady of Arantzazu in San Mateo, Rizal.