A new species of Protosticta Selys, 1885 (Odonata: Zygoptera: Platystictidae) is described based on two male specimens collected from Kerala, at the southern end of the Western Ghats in India. We compared P. armageddonensis sp. nov. with the three closely similar Protosticta species recently described from the Western Ghats, namely P.anamalaica Sadasivan, Nair & Samuel, 2022, P. cyanofemora Joshi, Subramanian, Babu & Kunte, 2020, and P. monticola Emiliyamma & Palot, 2016, to provide comprehensive differential diagnosis. The new species is distinguished from its congeners by a combination of characters, including the structure of prothorax, caudal appendages, genital ligula, and markings on the 8th abdominal segment. A revised key of Protosticta spp. of the Western Ghats, based on mature male specimens is provided.