Summary: Functional gastrointestinal disorders, including irritable bowel syndrome, are currently referred to as disorders of the gut-brain axis. Irritable bowel syndrome is one of the two most common disorders in this group, alongside functional dyspepsia. The global prevalence of IBS is approximately 11% of the world's population, although this varies between countries and geographical regions. It causes significant discomfort that reduces the quality of life of patients and often makes it difficult to differentiate from organic diseases. The diagnosis is based on the Rome IV criteria, but in the case of alarm symptoms, family history, and patients over 50 years of age, further diagnosis is necessary. Genetic, environmental, and psychosocial factors, intestinal microbiota disorders and the microinflammation they cause, motility disorders, and visceral hypersensitivity play a role in the pathogenesis. Due to the lack of a single etiological factor, the treatment of IBS consists in reducing the severity of symptoms and improving the quality of life of patients, taking into account the pursuit of beneficial modification of the intestinal microbiota, which seems to be an important therapeutic goal. Symptomatic pharmacotherapy involves the use of antispasmodic drugs that regulate motility. Antidepressants have also been shown to be effective as a second-line treatment, confirming that functional disorders are a manifestation of disturbances in the gut-brain axis. Given the important role of the gut microbiota, strategies for its beneficial modification include dietary management, the use of eubiotics that are not absorbed from the gastrointestinal tract (rifaximin), and probiotic therapy using strains tested in randomized clinical trials with proven efficacy. Microbiota transplantation from a healthy donor is still not a recommended therapeutic approach for this indication.