Atopic dermatitis (AD) is a skin condition that may cause a rash and itching due to inflammation of the skin. This study will assess how safe and effective upadacitinib is in treating AD in adolescent and adult Chinese participants. Upadacitinib is an approved drug for treating AD. Approximately 200 adolescent and adult participants who are prescribed upadacitinib by their physician in accordance with local label will be enrolled in China. Participants will receive upadacitinib as prescribed by their physician according to their routine clinical practice and local label. Participants will be followed up for approximately 24 months per participant and 30 days after last treatment dose for safety data collection. 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