Oases have served as sacred landscapes and sources of ritual plants in arid regions of the Old and New Worlds. We evaluate the Jesuit mission oases of the Baja California peninsula for their role in agrobiodiversity persistence, and extend theories of sacred landscapes and biodiversity conservation to agricultural species and practices. Jesuit missionaries on the peninsula introduced a suite of crops species and agricultural and water management systems that persist in the oases and have become an integral part of the (...) cultural and religious identity of the peninsula. The sacred landscapes of the oases are defined by elements of the Jesuit mission systems, such as water capture systems and irrigation canals, stone field borders and terraces, field gardens or huertas, groves of olive trees and date palms, and multi-tiered agroecosystems. Sacred practices—including pilgrimages, religious rites, and Catholic-based community celebrations—depend on the integrated “landscapes” of the oases and on the ritual use of wild and cultivated oasis plant species. We propose that some, though not all, of the peninsula oases may be considered as sacred landscapes responsible for maintaining heritage crop species, biodiversity, and traditional farming and foodways practices. (shrink)