This is a real-life, multicenter, retrospective observational study with the aim to evaluate effectiveness and safety of Mirikizumab in a real life setting from the baseline up to manteinance at 12, 24 and 52 weeks. Patients with UC who have started mirikizumab will be included. Patients \> 18 years, with no distinction based on age, demographic group, special population, or general health status will be included. Eligible patients will be identified at each participating center among those receiving mirikizumab as part of routine clinical practice.The primary objective of this study is to evaluate the effectiveness of treatment in achieving clinical remission at week 12, as well as endoscopic remission at weeks 24 and 52. The secondary objectives are to assess changes over time in clinical, biochemical, and imaging parameters. Specifically, the study will evaluate changes in bowel urgency as measured by the Urgency Numeric Rating Scale (NRS), as well as changes in fecal calprotectin and C-reactive protein (CRP) levels from baseline to weeks 12, 24, and 52.