An overview of mucosal immunity, focusing on the unique immunological challenges and adaptations within the gastrointestinal tract. Outlinea the key immune cells, molecules, and tissues involved in protecting the gut lining, contrasting these responses with systemic immunity. Discusses diseases arising from inappropriate mucosal immune responses, including food allergies, inflammatory bowel disease (IBD), celiac disease, and certain immunodeficiencies. It also touches upon the emerging role of the gut microbiome in health and disease.