Plant growth-promoting rhizobacteria (PGPR) are soil bacteria that enhance plant growth through various mechanisms, including phosphate solubilization, nitrogen fixation, and production of plant hormones. These bacteria can replace chemical fertilizers and pesticides in agriculture, offering sustainable solutions. PGPR can be classified into extracellular (ePGPR) and intracellular (iPGPR) types based on their location within the plant. ePGPR reside in the rhizosphere or on root surfaces, while iPGPR live inside root cells. Many bacterial genera, such as Agrobacterium, Azotobacter, and Pseudomonas, are ePGPR. iPGPR include endophytes and Frankia, which symbiotically fix atmospheric nitrogen. PGPR can promote plant growth directly through nutrient solubilization or indirectly by stimulating mycorrhizae development. They also exhibit antifungal activity and induce systemic resistance in plants. PGPR have been used in various agricultural applications, including disease control and soil fertility improvement. Recent research has focused on understanding the diversity and mechanisms of PGPR in the rhizosphere. These bacteria are important components of sustainable agricultural systems due to their ability to enhance plant growth and reduce the need for chemical inputs. The review summarizes the current understanding of PGPR, their mechanisms of action, and their potential in agriculture.Plant growth-promoting rhizobacteria (PGPR) are soil bacteria that enhance plant growth through various mechanisms, including phosphate solubilization, nitrogen fixation, and production of plant hormones. These bacteria can replace chemical fertilizers and pesticides in agriculture, offering sustainable solutions. PGPR can be classified into extracellular (ePGPR) and intracellular (iPGPR) types based on their location within the plant. ePGPR reside in the rhizosphere or on root surfaces, while iPGPR live inside root cells. Many bacterial genera, such as Agrobacterium, Azotobacter, and Pseudomonas, are ePGPR. iPGPR include endophytes and Frankia, which symbiotically fix atmospheric nitrogen. PGPR can promote plant growth directly through nutrient solubilization or indirectly by stimulating mycorrhizae development. They also exhibit antifungal activity and induce systemic resistance in plants. PGPR have been used in various agricultural applications, including disease control and soil fertility improvement. Recent research has focused on understanding the diversity and mechanisms of PGPR in the rhizosphere. These bacteria are important components of sustainable agricultural systems due to their ability to enhance plant growth and reduce the need for chemical inputs. The review summarizes the current understanding of PGPR, their mechanisms of action, and their potential in agriculture.