A new species of damselfly, Teinobasis taripu sp. nov., is described from Bougainville Island in the Solomon Islands Archipelago. The male most closely resembles T. bradleyi Kimmins, 1957, which is known from several islands in the archipelago and occurs in sympatry with the new species on Bougainville. However, the new species can be distinguished from T. bradleyi by having a largely metallic black thorax speckled with yellowish brown (vs a more discrete pattern of metallic black and light blue), and by having a trilobed (vs unilobed) mid-dorsal appendix of abdominal segment 10. The new species is described, illustrated and diagnosed, and a key to the males of all Teinobasis species known from the Solomon Islands Archipelago is presented.