C. mertensii

C. mertensii may refer to:
 * Carex mertensii, the Mertens' sedge, a plant species
 * Chaetoceros mertensii, H.L. Honigmann, a marine planktonic diatom species in the genus Chaetoceros
 * Chaetodon mertensii, the atoll butterflyfish, a species of butterflyfish found in the Pacific Ocean