Nonalcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated steatotic liver disease (MASLD) are significant public health concerns, with NAFLD being a major cause of liver disease. The gut-liver axis, which describes the bidirectional interaction between the gut microbiota and the liver, plays a crucial role in the pathogenesis of these conditions. Alterations in gut microbiota and gut dysbiosis have been increasingly recognized as key factors in the development of NAFLD/MASLD. This review discusses the role of the gut-liver axis in the pathogenesis of NAFLD/MASLD and explores therapeutic options, including probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT). The gut-liver axis involves the gut epithelial, vascular, and immunological barriers, and the liver circulation. The gut barrier is maintained by a mucus layer and tight junctions (TJs), which prevent the entry of pathogens while allowing nutrient absorption. Gut dysbiosis, characterized by changes in the composition and diversity of the gut microbiota, can lead to increased gut permeability and the entry of harmful substances into the liver, contributing to inflammation and liver damage. The gut microbiota also influences the production of trimethylamine (TMA) and trimethylamine N-oxide (TMAO), which are associated with the progression of NAFLD/MASLD. Probiotics, defined as live microorganisms that confer health benefits, have been studied for their potential in treating NAFLD/MASLD. Various probiotic strains, such as Lactobacillus and Bifidobacterium, have shown promise in improving liver function and reducing inflammation. However, the effectiveness of probiotics in human trials has been inconsistent. Next-generation probiotics, such as Akkermansia muciniphila and Faecalibacterium prausnitzii, are being investigated for their potential to restore gut microbiota balance and improve liver health. Prebiotics, which are non-viable compounds that promote the growth of beneficial gut microbes, have also been studied for their role in NAFLD/MASLD. They work by increasing the production of short-chain fatty acids (SCFAs), which have anti-inflammatory and protective effects on the gut barrier. Synbiotics, which combine probiotics and prebiotics, have shown potential in reducing de novo lipogenesis and improving liver function. FMT has shown promise in restoring gut microbiota balance in patients with NAFLD/MASLD, particularly in lean patients with limited treatment options. However, safety concerns and the need for more research remain. The effectiveness of FMT in treating NAFLD/MASLD is still under investigation, and further studies are needed to confirm its benefits and safety. In conclusion, the gut microbiome plays a critical role in the pathogenesis of NAFLD/MASLDNonalcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated steatotic liver disease (MASLD) are significant public health concerns, with NAFLD being a major cause of liver disease. The gut-liver axis, which describes the bidirectional interaction between the gut microbiota and the liver, plays a crucial role in the pathogenesis of these conditions. Alterations in gut microbiota and gut dysbiosis have been increasingly recognized as key factors in the development of NAFLD/MASLD. This review discusses the role of the gut-liver axis in the pathogenesis of NAFLD/MASLD and explores therapeutic options, including probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT). The gut-liver axis involves the gut epithelial, vascular, and immunological barriers, and the liver circulation. The gut barrier is maintained by a mucus layer and tight junctions (TJs), which prevent the entry of pathogens while allowing nutrient absorption. Gut dysbiosis, characterized by changes in the composition and diversity of the gut microbiota, can lead to increased gut permeability and the entry of harmful substances into the liver, contributing to inflammation and liver damage. The gut microbiota also influences the production of trimethylamine (TMA) and trimethylamine N-oxide (TMAO), which are associated with the progression of NAFLD/MASLD. Probiotics, defined as live microorganisms that confer health benefits, have been studied for their potential in treating NAFLD/MASLD. Various probiotic strains, such as Lactobacillus and Bifidobacterium, have shown promise in improving liver function and reducing inflammation. However, the effectiveness of probiotics in human trials has been inconsistent. Next-generation probiotics, such as Akkermansia muciniphila and Faecalibacterium prausnitzii, are being investigated for their potential to restore gut microbiota balance and improve liver health. Prebiotics, which are non-viable compounds that promote the growth of beneficial gut microbes, have also been studied for their role in NAFLD/MASLD. They work by increasing the production of short-chain fatty acids (SCFAs), which have anti-inflammatory and protective effects on the gut barrier. Synbiotics, which combine probiotics and prebiotics, have shown potential in reducing de novo lipogenesis and improving liver function. FMT has shown promise in restoring gut microbiota balance in patients with NAFLD/MASLD, particularly in lean patients with limited treatment options. However, safety concerns and the need for more research remain. The effectiveness of FMT in treating NAFLD/MASLD is still under investigation, and further studies are needed to confirm its benefits and safety. In conclusion, the gut microbiome plays a critical role in the pathogenesis of NAFLD/MASLD