Inclusion Criteria:  Clinical diagnosis of r-axSpA upon physician's judgement. Physician decision on participant treatment with upadacitinib must have been reached prior to and independently of recruitment in the study. Upadacitinib prescribed in accordance with the local label.  Exclusion Criteria:  Prior exposure to any Janus kinase (JAK) inhibitor (including but not limited to upadacitinib, tofacitinib, baricitinib, and filgotinib). Participants with primary fibromyalgia (upon physician´s judgement) Participation in a clinical trial of an investigational drug, concurrently or within the last 30 days or five half-lives of the drug (whichever is longer) prior to the first dose of study drug or is currently enrolled in another clinical study. Participants who cannot be treated with upadacitinib according to the applicable local label.