To describe the effectiveness, treatment patterns, quality of life, and safety of participants with moderately or severely active UC treated with filgotinib in a real-world setting.

Inclusion Criteria:

1. Filgotinib-naïve participants with moderately or severely active UC as judged by the physician and starting filgotinib treatment according to local treatment guidelines, routine practices and product information.

Exclusion Criteria:

1. Participation in any interventional or non-interventional study without prior approval from the medical leader. This does not preclude inclusion of participants enrolled to national registries.
2. Participant is diagnosed with Crohn's disease.

The study population will consist of participants aged 18 years or older with moderately or severely active UC as judged by the physician and starting filgotinib treatment. Participants are enrolled across around 10 countries in Europe, including the United Kingdom.