S. tonkinensis may refer to:
Scaphis tonkinensis, an air-breathing sea slug species Sindora tonkinensis, a legume species found in Cambodia and Vietnam Sinogastromyzon tonkinensis, a ray-finned fish species Sophora tonkinensis, a plant species used in traditional Chinese medicine. Strobilanthes tonkinensis, a species of herbaceous plant used as a flavoring for tea native to Southeast Asia