Diols represent a crucial class of bulk chemicals with extensive applications across the polymer, cosmetics, fuel, food, and pharmaceutical industries. Developing biological routes to produce diols from renewable feedstocks such as biomass and C1 substrates is of great significance for reducing dependence on fossil resources and mitigating carbon dioxide emissions and has therefore attracted widespread attention in recent years. Although the biomanufacturing of some diols has been successfully commercialized, cost-effective bioproduction of most other diols remains challenging. Primary bottlenecks include the lack of efficient natural biosynthetic pathways and the low productivity of engineered strains. This review comprehensively summarizes recent advances in the microbial synthesis of diols, with a particular focus on the development of novel metabolic pathways and metabolic engineering strategies aimed at achieving efficient biosynthesis of C2 to C6 diols. Furthermore, we discuss the current state and major challenges associated with translating these biosynthetic processes into industrial applications, as well as future development prospects.