Soil supports diverse life forms and ecosystems through complex interactions among its components, many of which remain poorly understood. Potassium (K) is a vital macronutrient that plays an essential role in plant growth, enzymatic activities, and stress tolerance, but its bioavailability in soils is limited due to complexation in minerals, such as muscovite, biotite, and feldspars. Therefore, only a small fraction is in exchangeable, plant-accessible form. While K fertilizers are commonly used in agriculture and agroforestry to address K deficiencies, the contributions of soil microbial communities to K solubilization and plant acquisition are increasingly recognized. Soil microbes, including K-solubilizing fungi and bacteria, enhance nutrient availability by decomposing soil components, facilitating K release and plant uptake. Despite early recognition of microbial K solubilization in the late nineteenth century, the role of microbes in supporting plant K acquisition remains underexplored, particularly in natural and agro-ecosystems. This chapter reviews current knowledge on plant K uptake mediated by soil microbes, including endophytic and K-solubilizing fungi, bacteria, and mycorrhizal fungi, to highlight their potential for improving soil K cycling, plant K-use-efficiency, and sustainable agricultural practices.