Ulcerative colitis (UC) is a type of inflammatory bowel disease that causes inflammation and bleeding from the lining of the rectum and colon (large intestine). This study will assess the change in disease activity of risankizumab treatment in adult participants with moderate to severe UC in real-world clinical practice. Risankizumab is an approved drug for treating participants with ulcerative colitis. Approximately 200 participants who are prescribed risankizumab by their physician in accordance with local label will be enrolled in approximately 30 sites across Japan. Participants will receive risankizumab as prescribed by their physician according to their routine clinical practice and local label. Participants will be followed for up to 156 weeks. There is expected to be no additional burden for participants in this trial. Participants will attend regular visits during the study at a hospital or clinic according to their routine clinical practice.