Soil salinity is a major abiotic stress limiting plant growth and crop productivity worldwide. Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plant roots and have emerged as effective bio-ameliorators of salt stress. This chapter synthesizes current knowledge on how AMF improve plant salt tolerance through multiple interrelated mechanisms. AMF symbiosis enhances the host plant’s nutrient and water uptake capacity, helping to maintain growth under saline conditions. It also promotes ionic homeostasis by regulating uptake and distribution of Na+ and K+, thereby protecting vital metabolic processes. Mycorrhizal plants often show higher photosynthetic rates and chlorophyll content under salt stress, along with increased activities of antioxidant enzymes that mitigate oxidative damage. AMF can induce osmoprotective responses (e.g. accumulation of proline, glycine betaine) and modulate phytohormone levels to further bolster stress resilience. Case studies across diverse plant species and meta-analyses of hundreds of trials confirm that AMF generally confer significant benefits in saline environments, from improved biomass production to reduced salt injury, although the magnitude of these effects can depend on plant type, AMF species, and salinity severity. Harnessing AMF in agriculture offers a sustainable strategy to alleviate salinity stress and maintain crop yields in salt-affected soils.