<p>Chronic obstructive pulmonary disease (COPD), the third leading cause of mortality worldwide, is a heterogeneous disorder characterized by airway inflammation and progressive decline in lung function. While current therapies provide symptomatic relief, they fail to modify disease progression, with early diagnosis remaining challenging due to nonspecific clinical presentations. Emerging evidence has established the gut microbiota as a vital modulator of COPD pathogenesis via the microbiota-gut-lung axis, which is mediated through dysregulated short-chain fatty acid metabolism, bidirectional inflammatory cytokine regulation, and compromised mucosal barrier integrity. Clinically, COPD patients exhibit significantly reduced gut microbial diversity, and the dynamic Bacteroidetes/Firmicutes ratio has emerged as a promising early diagnostic biomarker. This comprehensive review synthesizes recent five-year evidence to elucidate gut-lung axis mechanisms, identify novel microbial biomarkers for early prediction, and evaluate microbiota-targeted therapeutic interventions, ultimately providing new scientific frameworks for developing targeted strategies for COPD prevention and clinical management.</p>