Sant Pere d'Ullastre is a Romanesque chapel from the 10th-11th centuries located on the left bank of the Torrent de Colobrers near the headwaters of the Tort River, in the southern half of the municipality of Castellar del Vallés. It is a protected work as a cultural asset of local interest. The church is currently attached to the west side of the Can Santpere farmhouse.
The hermitage is popularly known by the name of Sant Pere de la cadireta, since an image of Saint Peter seated on the throne is venerated. The location of an ullastreda next to the Can Santpere farmhouse suggests, on the other hand, that the hermitage receives its name from the presence in the area of this variety of olive trees, typical of land close to the Mediterranean.
There is news of the existence of the temple at least since 1012, the year in which the approval of a public deed between the Berenguer brothers and Arnau Santpere took place.
The chapel has been part of the municipal architectural heritage since the end of 2004, the date on which the owner made the donation to the town hall.