This is a prospective, multicenter, randomized clinical evaluation of the Sphere-9 Mapping and Ablation Catheter with the Affera Mapping and Ablation System. Subjects will be randomly assigned 1:1 to receive treatment with either the Sphere-9 Mapping and Ablation Catheter and the Affera Mapping and Ablation System (investigational device) or the THERMOCOOL SMARTTOUCH® SF radiofrequency ablation catheter (control device).

Inclusion Criteria:

1. Symptomatic PerAF documented by (1) a physician's note indicating symptoms consistent with AF sustained longer than 7 days but less than 12 months; AND either (2a) a 24-hour Holter documenting continuous AF within the past year OR (2b) two electrocardiograms (from any form of rhythm monitoring, including consumer devices) taken at least 7 days apart within the past year, each showing continuous AF.
2. Failure or intolerance of at least one Class I or III anti-arrhythmic drug (AAD).
3. Suitable candidate for catheter ablation.
4. Adults aged 18 - 80 years.
5. Willing and able to comply with all baseline and follow-up evaluations for the full length of the study.
6. Willing and able to provide informed consent.

Exclusion Criteria:

1. Continuous AF lasting for 12 months or longer.
2. AF secondary to electrolyte imbalance, thyroid disease, acute alcohol intoxication, or other reversible or non-cardiac cause.
3. Previous left atrial ablation or surgical procedure (including septal closure or left atrial appendage closure).
4. Valvular cardiac surgical/percutaneous procedure (e.g., ventriculotomy, atriotomy, and valve repair or replacement and presence of a prosthetic valve).
5. Any carotid stenting or endarterectomy.
6. Any cardiac procedure (surgical or percutaneous) or percutaneous coronary intervention within the 90 days prior to the initial procedure.
7. Coronary artery bypass graft (CABG) procedure within the 6 months prior to the initial procedure.
8. Awaiting cardiac transplantation or other cardiac surgery within the 12 months following the initial ablation procedure.
9. Presence of a permanent pacemaker, biventricular pacemaker, or any type of implantable cardiac defibrillator (with or without biventricular pacing function).
10. Documented thromboembolic event (stroke or transient ischemic attack) within 6 months (180 days) prior to the initial ablation procedure.
11. Documented left atrial thrombus on imaging.
12. History of blood clotting or bleeding abnormalities.
13. Any condition contraindicating chronic anticoagulation.
14. Myocardial infarction (MI) within the 3 months (90 days) prior to the initial procedure.
15. Body mass index >40 kg/m2.
16. Left atrial diameter >55 mm (anterioposterior).
17. Diagnosed atrial myxoma.
18. Left ventricular ejection fraction (EF) < 35%.
19. Uncontrolled heart failure or NYHA Class III or IV heart failure.
20. Rheumatic heart disease.
21. Hypertrophic cardiomyopathy.
22. Unstable angina.
23. Moderate to severe mitral valve stenosis.
24. Severe mitral regurgitation (regurgitant volume ≥ 60 mL/beat, regurgitant fraction ≥ 50%, and/or effective regurgitant orifice area ≥ 0.40cm2).
25. Primary pulmonary hypertension.
26. Significant restrictive or obstructive pulmonary disease or chronic respiratory condition.
27. Renal failure requiring dialysis.
28. History of severe Gastroesophageal Reflux Disease (GERD) requiring surgical and/or mechanical intervention.
29. Acute illness, active systemic infection, or sepsis.
30. Contraindication to both computed tomography and magnetic resonance angiography.
31. Significant congenital anomaly or medical problem that, in the opinion of the investigator, would preclude enrollment in this study or compliance with follow-up requirements or would impact the scientific soundness of the clinical study results.
32. Any woman known to be pregnant or breastfeeding, or any woman of childbearing potential who is not on a reliable form of birth regulation method or abstinence.
33. Current or anticipated participation in any other clinical study of a drug, device, or biologic during the duration of the study not pre-approved by the Sponsor.
34. Presence of intramural thrombus, tumor, or other abnormality that precludes vascular access, catheter introduction, or manipulation.
35. Known drug or alcohol dependency.
36. Life expectancy less than 12 months.
37. Vulnerable subject (such as a prisoner or handicapped or mentally disabled person).

Subjects will be blinded to treatment assignment