Interactions between microbial communities and the host can modulate mosquito biology, including vector competence. Therefore, future vector biocontrol measures will utilize these interactions and require extensive monitoring of the mosquito microbiome. Metabarcoding strategies will be useful for conducting vector monitoring on a large scale. We used 16S and 18S rRNA gene metabarcoding through iSeq100 sequencing to characterize the microbiome and eukaryome of Aedes albopictus (Skuse 1894) and Culex pipiens (Linnaeus 1758), two globally important vectors present in South Korea. Mosquitoes were collected from an urban and a semi-urban location in South Korea. Bacterial alpha and beta diversities varied by population. Pseudomonadota dominated the microbiomes of both species. The microbiome composition varied by population and was dominated by different taxa. At the genus level, Wolbachia sp. was the most enriched genus in Cx. pipiens, followed by Aeromonas sp. In Ae. Albopictus, the most abundant group was Enterococcus sp. The gregarine parasite Ascogregarina taiwanensis was highly prevalent in Ae. Albopictus and its absence was marked by the presence of seven bacterial taxa. To our knowledge, this is the first characterization of the microbiome of Ae. albopictus and Cx. pipiens in these regions of South Korea and contributes to the current information on the microbiome of mosquito species, which can be used in further studies to assess pathogen-microbiome and microbiome-microbiome interactions.