This systematic review explores the prevalence, diversity, and potential applications of nodule endophytic bacteria in legumes. The study identifies Bacillus and Pseudomonas as the most prevalent genera of nodule endophytic bacteria, followed by Paenibacillus, Enterobacter, Pantoea, Agrobacterium, and Microbacterium. These bacteria are primarily associated with Glycine max (soybean), Vigna radiata (mung bean), Phaseolus vulgaris (common bean), and Lens culinaris (lentils). Clustering analysis confirms the dominance of Bacillus and Pseudomonas in nodule endophytic communities, alongside Paenibacillus, Agrobacterium, and Enterobacter. Although non-rhizobial endophytes do not induce nodule formation, they contribute to plant growth-promoting properties (PGPs), including phytostimulation, biofertilization, biocontrol, and stress tolerance. These properties are crucial for enhancing legume growth and resilience. The interaction between non-rhizobial and rhizobial bacteria within nodules can influence leguminous host plants, with co-inoculation often leading to synergistic effects on plant growth, yield, and nodulation. These effects are pronounced under both stress and non-stress conditions, surpassing the impact of single inoculations with rhizobia alone. The review highlights the diversity of non-rhizobial endophytic bacteria in legume nodules, including genera such as Agrobacterium, Klebsiella, Paenibacillus, Bacillus, Blastobacter, Dyadobacter, Phyllobacterium, Pseudomonas, Ensifer, and Enterobacter. These bacteria exhibit various beneficial activities, such as synthesizing plant hormones, fixing atmospheric nitrogen, solubilizing inorganic phosphate, and enhancing the catalytic activity of ACC deaminase, underscoring their potential for sustainable agriculture. Despite these documented benefits, there is a lack of comprehensive understanding regarding nodule endophytes across various ecological niches, including desert plants. This gap in knowledge extends to their diversity, activities, and effects on plant tolerance and growth under stressful conditions. The study also discusses the role of nodule endophytes in biofertilization, stress tolerance, biocontrol, and phytostimulation. Nodule endophytes contribute to nitrogen fixation, phosphate solubilization, and siderophore production, which enhance plant growth and nutrient availability. They also play a role in stress tolerance by accumulating osmolytes and antioxidant compounds, and by exhibiting ACC deaminase activity. Additionally, nodule endophytes have biocontrol potential, as they can inhibit phytopathogens through the production of lytic enzymes, siderophores, and bacteriocins. Their ability to produce plant hormones such asThis systematic review explores the prevalence, diversity, and potential applications of nodule endophytic bacteria in legumes. The study identifies Bacillus and Pseudomonas as the most prevalent genera of nodule endophytic bacteria, followed by Paenibacillus, Enterobacter, Pantoea, Agrobacterium, and Microbacterium. These bacteria are primarily associated with Glycine max (soybean), Vigna radiata (mung bean), Phaseolus vulgaris (common bean), and Lens culinaris (lentils). Clustering analysis confirms the dominance of Bacillus and Pseudomonas in nodule endophytic communities, alongside Paenibacillus, Agrobacterium, and Enterobacter. Although non-rhizobial endophytes do not induce nodule formation, they contribute to plant growth-promoting properties (PGPs), including phytostimulation, biofertilization, biocontrol, and stress tolerance. These properties are crucial for enhancing legume growth and resilience. The interaction between non-rhizobial and rhizobial bacteria within nodules can influence leguminous host plants, with co-inoculation often leading to synergistic effects on plant growth, yield, and nodulation. These effects are pronounced under both stress and non-stress conditions, surpassing the impact of single inoculations with rhizobia alone. The review highlights the diversity of non-rhizobial endophytic bacteria in legume nodules, including genera such as Agrobacterium, Klebsiella, Paenibacillus, Bacillus, Blastobacter, Dyadobacter, Phyllobacterium, Pseudomonas, Ensifer, and Enterobacter. These bacteria exhibit various beneficial activities, such as synthesizing plant hormones, fixing atmospheric nitrogen, solubilizing inorganic phosphate, and enhancing the catalytic activity of ACC deaminase, underscoring their potential for sustainable agriculture. Despite these documented benefits, there is a lack of comprehensive understanding regarding nodule endophytes across various ecological niches, including desert plants. This gap in knowledge extends to their diversity, activities, and effects on plant tolerance and growth under stressful conditions. The study also discusses the role of nodule endophytes in biofertilization, stress tolerance, biocontrol, and phytostimulation. Nodule endophytes contribute to nitrogen fixation, phosphate solubilization, and siderophore production, which enhance plant growth and nutrient availability. They also play a role in stress tolerance by accumulating osmolytes and antioxidant compounds, and by exhibiting ACC deaminase activity. Additionally, nodule endophytes have biocontrol potential, as they can inhibit phytopathogens through the production of lytic enzymes, siderophores, and bacteriocins. Their ability to produce plant hormones such as