Inclusion Criteria:

1. The subject is of legal age to participate in the study per the laws of their respective geography.
2. The subject has documented paroxysmal, persistent, permanent or long-term/longstanding persistent non-valvular atrial fibrillation (i.e., the subject has not been diagnosed with rheumatic mitral valvular heart disease).
3. The subject is eligible for the defined protocol pharmacologic regimen of warfarin and antiplatelet therapy following WATCHMAN FLX Device implant.
4. The subject is eligible to come off warfarin therapy if the LAA is sealed (i.e., the subject has no other conditions that would require long-term warfarin therapy suggested by current standard medical practice).
5. The subject has a calculated CHADS2 score of 2 or greater or a CHA2DS2-VASc score of 3 or greater.
6. The subject is able to understand and willing to provide written informed consent to participate in the trial.
7. The subject is able and willing to return for required follow-up visits and examinations.

Exclusion Criteria:

1. Subjects who are currently enrolled in another investigational study or registry that would directly interfere with the current study, except when the subject is participating in a mandatory governmental registry, or a purely observational registry with no associated treatments. Each instance must be brought to the attention of the sponsor to determine eligibility, regardless of type of co-enrollment being proposed.
2. The subject requires long-term anticoagulation therapy for reasons other than AF-related stroke risk reduction, for example due to an underlying hypercoaguable state (i.e., even if the device is implanted, the subjects would not be eligible to discontinue warfarin due to other medical conditions requiring chronic warfarin therapy).
3. The subject is contraindicated for warfarin therapy.
4. The subject is contraindicated or allergic to aspirin.
5. Subject is contraindicated for clopidogrel (P2Y12 inhibitor for Japan).
6. The subject is indicated for clopidogrel (P2Y12 inhibitor for Japan) therapy or has taken clopidogrel (P2Y12 inhibitor for Japan) within 7 days prior to the WATCHMAN FLX Device implant.
7. The subject had or is planning to have any cardiac or non-cardiac invasive or surgical procedure within 30 days prior to or 60 days after the WATCHMAN FLX Device implant (including, but not limited to: cardioversion, coronary angiogram with or without percutaneous coronary intervention (PCI), cardiac ablation, cataract surgery, endoscopy, etc.).
8. The subject had a prior stroke (of any cause, whether ischemic or hemorrhagic) or transient ischemic attack (TIA) within the 90 days prior to enrollment.
9. The subject has had a myocardial infarction (MI) documented in the clinical record as either a non-ST elevation MI (NSTEMI) or as an ST-elevation MI (STEMI), with or without intervention, within 90 days prior to enrollment.
10. The subject has a history of atrial septal repair or has an ASD/PFO device.
11. The subject has an implanted mechanical valve prosthesis in any position.
12. The subject currently or has had any documented history of, New York Heart Association Class IV Congestive Heart Failure.
13. The subject is of childbearing potential and is, or plans to become pregnant during the time of the study (method of assessment upon study physician's discretion).