Inclusion Criteria:

• Male or female participants of any race aged at least 18 years at time of initiation of luspatercept treatment
• Participants with documented diagnosis of transfusion-dependent β-thalassemia (TDT).
• Participants who have been initiated on treatment with luspatercept as per the product's Summary of Product Characteristics (SmPC) no longer than 12 months prior to informed consent signature, and for whom therapy is ongoing.
• Participants for whom the decision to prescribe luspatercept treatment is clearly separated from the physician's decision to include the participant in the current study.
• Participants who have provided signed informed consent for participating in the study and for collecting and analyzing medical data pertinent to the objectives of this study

Exclusion Criteria:

• Participants that meet any of the contraindications to the administration of luspatercept as outlined in the latest version of the locally approved SmPC.
• Participants who are currently receiving or are planned to receive treatment with any investigational drug/device/intervention or who have received any investigational product within 1 month or 5 half-lives of the investigational agent (whichever is longer) prior to luspatercept therapy initiation.
• Participants who are currently pregnant, breastfeeding, or planning a pregnancy during the study observation period.
• Participants who have not provided signed informed consent for participating in the study and for collecting and analysing medical data pertinent to the objectives of this study.