**Abstract**

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory disorder that includes Crohn's disease and ulcerative colitis. Ulcerative colitis involves the distal colon, proximal colon, and cecum and can lead to ulcerations and bleeding. Crohn's disease appears as patched lesions in the gastrointestinal tract and inflammation, stenosis, or fistulas. IBD affects millions of people worldwide and has been associated with high morbidity and mortality. Our intestine is colonized by trillions of microorganisms (including bacteria, viruses, fungi, and protozoa), which constitutes the microbiota. Reduction of bacteria with anti-inflammatory capacities and increase of bacteria with inflammatory capacities are observed in patients with IBD when compared with healthy individuals. Microbial balance is needed for the development of a healthy gut and a symbiotic microbiota without problems. Any disturbance in that balance leads to dysbiosis and the host may become more susceptible to disease. Some alteration in the microbiome is protective or causative; thus, we selectively will review IBD disease, pathogenesis, and potential roles of some members of microbiota in IBD. In this chapter, we also explain the therapeutic approaches targeting microbiota (probiotics, prebiotics, postbiotics) and the relationship between gut microbiota imbalance, and how defects in this dysbiosis can lead to disease.

**Keywords:** inflammatory bowel disease, gut microbiome, Crohn's disease, ulcerative colitis, microbiome, dysbiosis, therapy
