O. orientalis

O. orientalis may refer to:
 * Octoknema orientalis, a plant species endemic to Tanzania
 * Onchidella orientalis, an air-breathing sea slug species
 * Orosius orientalis, the common brown leafhopper, a leafhopper species found in Australia
 * Ovis orientalis (or O. aries orientalis), the mouflon, a wild sheep species
 * Oxychilus orientalis, an air-breathing land snail species found in Slovakia