The gut microbiota exhibits intricate connections with the body's immune system and holds significant implications for various diseases and cancers. Currently, accumulating evidence suggests a correlation between the composition of the gut microbiota and the development, treatment, and prognosis of melanoma. However, the underlying pathogenesis remains incompletely elucidated. In this comprehensive review, we present an in-depth review of the role played by gut microbiota in melanoma tumorigenesis, growth, metastasis, treatment response, and prognosis. Furthermore, we discuss the potential utility of gut microbiota as a promising prognostic marker. Lastly, we summarize three routes through which gut microbiota influences melanoma: immunity, aging, and the endocrine system. By modulating innate and adaptive immunity in patients with melanoma across different age groups and genders, the gut microbiota plays a crucial role in anti-tumor immune regulation from tumorigenesis to prognosis management, thereby impacting tumor growth and metastasis. This review also addresses current study limitations while highlighting future research prospects.