Bacillus licheniformis is a spore-forming probiotic bacterium that has been studied for its role in supporting gastrointestinal health, including the small intestine. Scientific evidence indicates that B. licheniformis can survive the acidic environment of the stomach and reach the small intestine, where it may contribute to gut health by modulating the microbiota, enhancing digestive enzyme production, and exerting antimicrobial effects against certain pathogens. Several animal studies and a few human clinical trials have shown that supplementation with B. licheniformis can help restore gut microbial balance, improve intestinal barrier function, and reduce symptoms of gastrointestinal disturbances such as diarrhea. Its ability to inhibit harmful bacteria and support the proliferation of beneficial microbes suggests a role in maintaining the health of the small intestine. However, while the evidence is promising, it is not as extensive or robust as for some other probiotic strains, and more large-scale, high-quality human studies are needed to confirm its efficacy and safety for this specific use. Overall, current scientific data support a moderate level of evidence for using B. licheniformis to support the small intestine, particularly in the context of digestive health and microbiome modulation.