Nasal mites of the family Rhinonyssidae are parasites living in the respiratory system of birds. To date there were no record of these mites from representatives of the order Procellariiformes, a numerous grouping of exclusively marine birds that includes albatrosses, petrels, storm-petrels and shearwaters. The paper describes two new species of the genus Rhinonyssus from shearwaters (Procellariidae) found on various shores of Brazil: Rhinonyssus borealis sp. nov. from Calonectris borealis (Cory's shearwater) and R. procellaricus sp. nov. from Puffinus puffinus (Manx shearwater) and Ardenna gravis (Great shearwater). Both described mites are characterized by a large elliptical body and a relatively large and strongly sclerotized with the well-developed caudal extension. Rhinonyssus borealis sp. nov. and R. procellaricus sp. nov. are similar in their general appearance to each other but differ in the size of idiosoma, shape of podosomal and sternal shields and leg chaetotaxy.