Inclusion Criteria:

• 18 years of age or older.
• MR ≥ 3+.
• NYHA functional class ≥ II.
• Subject is at high or prohibitive risk for mitral valve surgery as determined by the Heart Team.
• table heart failure medication regimen for at least 30 days prior to enrollment.
• Note:  Subjects who require significant changes to heart failure medication after enrollment but prior to the procedure must re-stabilize for 30 days to be eligible.
• The subject has been informed of the nature of the study, agrees to its provisions and has provided written informed consent as approved by the Institutional Review Board / Ethics Committee of the respective clinical site.

Exclusion Criteria:

• Subject can be optimally treated with MitraClip per the approved indication.
• Mitral/cardiac anatomy that would preclude appropriate delivery and deployment of the dock or valve, including but not limited to:
  • Commissural diameter > 45 mm (as assessed by CT core lab);
  • Commissural flail;
  • Calcification that would interfere with the M3 System during delivery or after implantation;
  • Primary regurgitant jet at either commissure;
  • Interatrial septum or left atrium not suitable for transcatheter trans-septal access;
  • LVEDD ≥ 70 mm as assessed by echo core lab;
  • Left Ventricular End-Systolic Diameter (LVESD) < 35 mm as assessed by CT core lab;
• Inappropriate anatomy for femoral introduction and delivery of the SAPIEN M3 Dock and Valve.
• Presence of any device that will contact or interfere with the M3 System during delivery or after implantation.
• Significant risk of LVOT obstruction as assessed by CT core lab.
• Left Ventricular Ejection Fraction <30% as assessed by Echo core lab.
• Severe right ventricular dysfunction as assessed by Echo core lab.
• Need for aortic, tricuspid or pulmonic valve intervention.
• Severe tricuspid regurgitation requiring surgery.
• Status 1 for heart transplant or history of heart transplant.
• Cardiac imaging evidence of intracardiac mass, thrombus or vegetation.
• Active bacterial endocarditis within 180 days of the procedure.
• Hemodynamic instability requiring inotropic or mechanical support within 30 days of the procedure.
• Myocardial infarction within 30 days of the procedure.
• Clinically significant untreated coronary artery disease requiring revascularization.
• Any percutaneous cardiovascular intervention, cardiovascular surgery, or carotid surgery within 30 days of the procedure; transcatheter leaflet plication procedures are excluded regardless of timeframe (See Failed MitraClip Registry).
• Stroke or transient ischemic attack within 90 days of the procedure.
• Irreversible, severe pulmonary hypertension (e.g., pulmonary artery systolic pressure ≥ 2/3 systemic pressure).
• Chronic obstructive pulmonary disease (COPD) requiring home oxygen therapy or chronic outpatient oral steroid use.
• Renal insufficiency (estimated glomerular filtration rate, eGFR) per Cockcroft Gault formula < 30) or receiving renal replacement therapy.
• Liver disease (cirrhosis of the liver [Child-Pugh class B or C]).
• Planned surgery within the next 12 months.
• Inability to tolerate or a medical condition precluding treatment with antithrombotic therapy.
• Active infection requiring current antibiotic therapy (if temporary illness, subject may be a candidate 2 weeks after discontinuation of antibiotics).
• Leukopenia (White Blood Cells < 3000 cells/mL), anemia (Hemoglobin < 9 g/dL), thrombocytopenia (platelet < 50,000 cells/mL), history of bleeding diathesis or coagulopathy, or hypercoagulable states.
• Refusal of blood products.
• Female who is pregnant or lactating.
• Estimated life expectancy < 12 months due to non-cardiac conditions.
• Participating in another investigational drug or device study.