Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues, affecting millions of people and often requiring long-term treatment. Current therapies, such as immunosuppressants and biologics, help manage symptoms but can cause serious side effects. A promising new approach involves engineered microbiota-a method that modifies gut bacteria to influence immune function and potentially ease autoimmune conditions. The gut microbiome is crucial in regulating immunity, and imbalances in its composition have been linked to diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS), and inflammatory bowel disease (IBD). Engineered microbiota works by altering microbial communities, either by adding new strains, genetically modifying existing bacteria, or using carefully selected groups of microbes to control inflammation and immune responses. Recent studies in both animal models and human trials suggest this approach could help restore immune tolerance, reduce inflammation, and repair the gut barrier. However, challenges remain, including ensuring safety, long-term effectiveness, and meeting regulatory standards. Despite being in its early stages, engineered microbiota holds great promise as a future treatment for autoimmune diseases, paving the way for more precise and personalized therapies that leverage the power of the microbiome to improve health.