Microplastic (MP) pollution is an increasing environmental concern in coastal areas exposed to anthropogenic pressure, although its ecological and human-health implications depend on exposure, bioavailability, and potential effects. This study assesses MP contamination across seven beaches in the Gulf of Gabès, Tunisia, by integrating environmental characterization, polymer identification, and spatial analysis within the context of coastal sustainability. The mean MP abundance was 170.38 ± 17.14 items kg⁻¹ of dry sediment. Microplastics were characterized by shape, color, and size, with fibers and fragments being the most prevalent forms. Fourier-transform infrared spectroscopy (FTIR) identified polyethylene (PE), polypropylene (PP), and polystyrene (PS) among the analyzed particles. Some foam particles exhibited spectral features tentatively consistent with the antioxidant additive Cyanox 53; however, this assignment requires independent analytical confirmation. Spatial variability was explored using the Microplastic Pollution Index (MPPI), the Coefficient of Microplastic Impact (CMPI), hierarchical cluster analysis (HCA), and principal component analysis (PCA). Based on the adopted MPPI classification scheme, five beaches were classified as high, one as very high, and one as moderate. The observed spatial patterns may be associated with local anthropogenic activities, including tourism, fishing, and waste discharge, although these potential sources were not directly investigated. The findings provide baseline information on MP contamination across the surveyed beaches and may inform future monitoring and coastal management initiatives relevant to Sustainable Development Goals 14, 12, and 8. The results should be interpreted in light of the study’s spatial and temporal scope and methodological limitations and should not be considered direct evidence of ecological effects or human-health risks.