Puffinus is a genus of seabirds in the order Procellariiformes. It comprises about 20 small to medium-sized shearwaters. Two other shearwater genera are named: Calonectris, which comprises three large shearwaters, and Procellaria with another four large species. The latter are usually called petrels, although they are thought to be more closely related to the shearwaters than to the other petrels.