Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) is a highly pathogenic tick-borne virus that causes hemorrhagic fever in humans, with a mortality rate of up to 30 %. SFTSV has been primarily detected in arachnid vectors, particularly Haemaphysalis longicornis. While the majority of human SFTSV infections are linked to tick exposure, a significant proportion of cases have no reported history of tick bites, suggesting the existence of alternative vectors. Here, we report the first detection of SFTSV RNA in deer ked (Lipoptena fortisetosa, family Hippoboscidae) using reverse transcription-PCR (RT-PCR) and in situ hybridization (ISH), marking the first identification of SFTSV within the class Insecta. Phylogenetic analysis revealed that the detected viral RNA belongs to Genotype B-3, the predominant strain in South Korea, and Genotype D. Our surveillance findings suggest that deer ked may serve as a potential vector for SFTSV transmission to mammals. These findings highlight the need for further epidemiological and experimental studies to assess their role in virus transmission dynamics.