Inclusion Criteria:

• The subject is of legal age to participate in the study per the laws of their respective geography.
• 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).
• The subject has a calculated CHA2DS2-VASc score of 2 or greater.
• The subject is deemed by two study physicians to be unsuitable for oral anticoagulation.
• The subject is deemed by a study physician to be suitable for the defined protocol pharmacologic regimen of aspirin and clopidogrel therapy following WATCHMAN Closure Device implant.
• The subject or legal representative is able to understand and willing to provide written informed consent to participate in the trial.
• The subject is able and willing to return for required follow-up visits and examinations.

Exclusion Criteria:

• The subject is unable or unwilling to return for required follow-up visits and examinations.
• The subject had or is planning to have any invasive cardiac procedure within 30 days prior to randomization (e.g., cardioversion, ablation).
• The subject is planning to have any cardiac or non-cardiac invasive or surgical procedure that would necessitate stopping or modifying the protocol required medication regimen within 90 days after the WATCHMAN Closure Device implant (e.g., cardioversion, ablation, cataract surgery).
• The subject had a prior stroke (of any cause) or TIA within the 30 days prior to randomization.
• The subject had a prior BARC type 3 or 4 bleeding event within the 14 days prior to randomization. Lack of resolution of related clinical sequelae, or planned and pending interventions to resolve bleeding/bleeding source, are a further exclusion regardless of timing of the bleeding event.
• The subject has a history of atrial septal repair or has an ASD/PFO device.
• The subject has an implanted mechanical valve prosthesis in any position.
• The subject suffers from New York Heart Association Class IV Congestive Heart Failure.
• The subject has LVEF < 30%.
• 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).
• The subject is 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 should be brought to the attention of the sponsor to determine eligibility.
• The subject has a life expectancy of less than two years.
• The subject has a known or suspected hypercoagulable state.