Mirikizumab is a monoclonal antibody directed against the p19 subunit of interleukin (IL)-23 to inhibit its interaction with the IL-23 receptor. IL-23 is a key cytokine involved in initiating and perpetuating the inflammatory cascade in inflammatory bowel disease (IBD). Mirikizumab is the first agent from the novel anti-IL-23p19 drug class to be licensed for ulcerative colitis and the first to present long-term endoscopic, histologic, symptomatic, and quality-of-life outcomes. More recently, the VIVID trial programme has led to the approval of mirikizumab in moderate to severe Crohn's disease. This review explores the history of its development, discusses key immunopharmacological properties unique to the drug, and details the available clinical trials and real-world evidence supporting its use in IBD.