This review outlines the microbial degradation of polycyclic aromatic hydrocarbons (PAHs). A diverse microbial community, including bacteria, fungi, and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of PAHs by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than for catabolism and assimilation. The biochemical principles underlying PAH degradation are discussed in detail, along with the pathways of PAH catabolism. The relationship between the chemical structure of PAHs and their biodegradation rates in aquatic and terrestrial ecosystems is also examined. PAHs are hazardous organic chemicals composed of three or more fused benzene rings. They are primarily formed from fossil fuel combustion, industrial processes, and food cooking. PAHs enter the environment through various sources, including industrial effluents, sewage, and natural sources. PAHs are hydrophobic and persist in ecosystems due to their low water solubility. They can become associated with sediments, where they may persist until degraded, resuspended, bioaccumulated, or removed by dredging. The lipophilicity, environmental persistence, and genotoxicity of PAHs increase with molecular size, up to 4 or 5 fused benzene rings. Toxicological concern shifts towards chronic toxicity, primarily carcinogenesis. The possible fates of PAHs in the environment include volatilization, photooxidation, chemical oxidation, bioaccumulation, adsorption to soil particles, leaching, and microbial degradation. PAH concentrations vary widely depending on industrial development and petroleum product contamination. PAH contamination ranges from 5 ng/g in an undeveloped area to 1.79 × 10^6 ng/g at an oil refinery. Marine sediments can have PAH concentrations exceeding 10^5 ng/g in urban estuaries. Creosote is a major source of PAH contamination, as PAHs represent approximately 85–90% of creosote constituents. Microbiological degradation of PAHs is the major process leading to decontamination of sediment and surface soil. These compounds can be totally degraded (mineralized) or partially transformed by microbial communities or single microorganisms.This review outlines the microbial degradation of polycyclic aromatic hydrocarbons (PAHs). A diverse microbial community, including bacteria, fungi, and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of PAHs by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than for catabolism and assimilation. The biochemical principles underlying PAH degradation are discussed in detail, along with the pathways of PAH catabolism. The relationship between the chemical structure of PAHs and their biodegradation rates in aquatic and terrestrial ecosystems is also examined. PAHs are hazardous organic chemicals composed of three or more fused benzene rings. They are primarily formed from fossil fuel combustion, industrial processes, and food cooking. PAHs enter the environment through various sources, including industrial effluents, sewage, and natural sources. PAHs are hydrophobic and persist in ecosystems due to their low water solubility. They can become associated with sediments, where they may persist until degraded, resuspended, bioaccumulated, or removed by dredging. The lipophilicity, environmental persistence, and genotoxicity of PAHs increase with molecular size, up to 4 or 5 fused benzene rings. Toxicological concern shifts towards chronic toxicity, primarily carcinogenesis. The possible fates of PAHs in the environment include volatilization, photooxidation, chemical oxidation, bioaccumulation, adsorption to soil particles, leaching, and microbial degradation. PAH concentrations vary widely depending on industrial development and petroleum product contamination. PAH contamination ranges from 5 ng/g in an undeveloped area to 1.79 × 10^6 ng/g at an oil refinery. Marine sediments can have PAH concentrations exceeding 10^5 ng/g in urban estuaries. Creosote is a major source of PAH contamination, as PAHs represent approximately 85–90% of creosote constituents. Microbiological degradation of PAHs is the major process leading to decontamination of sediment and surface soil. These compounds can be totally degraded (mineralized) or partially transformed by microbial communities or single microorganisms.