A new species of Protosticta Selys, 1885 is described based on specimens collected from Kerala, northeast of Thiruvananthapuram, in the southern parts of the southern Western Ghats of India. Protosticta armageddonia sp. nov. is compared with all other known Protosticta species of the Western Ghats to provide comprehensive differential diagnosis. The new species is distinguished from its congeners by a combination of characters, including a marking on the ventral side of thorax, structure and colour of the prothorax, markings on the 8th abdominal segment, and the structure of caudal appendages and genital ligula. Furthermore, we provide preliminary information on the ecology and natural history of the new species.