Crohn's disease (CD) is an incurable chronic inflammatory disorder of the gastrointestinal tract. This study will assess how safe and effective upadacitinib is in treating moderately to severely active CD in real world. Speed of onset and durability of effectiveness will be assessed. Upadacitinib is a drug approved for the treatment of CD. All study participants will receive upadacitinib as prescribed by their study doctor in accordance with approved local label. Approximately 1200 participants will be enrolled in approximately 230 sites across the world. Participants will receive upadacitinib as prescribed by their physician according to their routine clinical practice and local label. Participants will be followed for up to 3 years. There is expected to be no additional burden for participants in this trial. Study visits may be conducted on-site or virtually as per standard of care.