The human gut microbiome, comprising trillions of microorganisms, plays a pivotal role in metabolic homeostasis. Emerging evidence implicates dysbiosis of the gut microbiota in the pathogenesis of type 2 diabetes mellitus (T2DM). This review synthesises current literature on the mechanistic links between microbiome composition and insulin resistance, inflammation, and gluconeogenesis. We examine findings from metagenomic studies, germ-free animal models, and fecal microbiota transplantation (FMT) experiments. The evidence supports a bidirectional relationship between glycaemic dysregulation and microbial imbalance. Therapeutic strategies including probiotics, prebiotics, synbiotics, and FMT are evaluated in the context of available clinical trial data. Future directions for microbiome-targeted interventions in T2DM management are discussed.