Koumiss is an acidic dairy beverage made from the raw milk of mares fermented by lactic acid bacteria and yeast, exhibiting country- and region-dependent differences. Koumiss development history dates back over a thousand years and this beverage has a broad consumer market in China, Russia, Europe, and Central Asia. Koumiss is rich in nutrients such as proteins, unsaturated fatty acids, vitamins, and minerals, and it displays multiple health benefits, including blood pressure- and cholesterol-reducing, parasitic disease treatment, antioxidant, sleep-improving, and immune regulatory effects. Research on koumiss fermentation as well as on the related strains and components has recently become a hot topic. However, the microbial diversity in koumiss, direct-vat starter development, industrial production, and the koumiss-related health benefits and underlying effector mechanisms require further exploration. To contribute to koumiss product development, this study summarised the key areas and hotspots in koumiss research and focused on the research progress related to the nutritional components, microbial diversity, health benefits, and production process of koumiss. This overview could help to identify bacterial types in koumiss, provide a reference for direct-vat starter development, and shed light on the health benefits of koumiss. Finally, this study would serve as a useful reference for koumiss quality control and koumiss product stability improvement.