| Marquis Bank | Florida |
| Marriott Employees Federal Credit Union | Maryland |
| Marseilles Bank | Illinois |
| Marshall Community Credit Union | Michigan |
| Marshall County Federal Credit Union | West Virginia |
| Marshall County State Bank | Minnesota |
| Marshall T & P Employees Federal Credit Union | Texas |
| Marshfield Medical Center Credit Union | Wisconsin |
| Marshland Community Federal Credit Union | Georgia |
| Martha's Vineyard Savings Bank | Massachusetts |
| Martin County Cooperative Credit Union | Indiana |
| Martin Federal Credit Union | Florida |
| Martin Luther King Credit Union | Texas |
| Martinsburg Bank and Trust | Missouri |
| Martinsburg VA Center Federal Credit Union | West Virginia |
| Martinsville First Savings Bank | Virginia |
| Marvel City Federal Credit Union | Alabama |
| Maryknoll of LA Federal Credit Union | California |
| Maryland Financial Bank | Maryland |
| Maryland Postal Federal Credit Union | Maryland |
| Maryvale Schools Federal Credit Union | New York |
| Maryville Municipal Credit Union | Tennessee |
| Mascoma Savings Bank | New Hampshire |
| Mason Bank | Texas |
| Mason City National Bank | Illinois |
| Mason County School Employees Credit Union | Michigan |
| Mason State Bank | Michigan |
| Maspeth Federal Savings and Loan Association | New York |
| Massachusetts Family Credit Union | Massachusetts |
| Mass Bay Credit Union | Massachusetts |
| Massena Savings and Loan | New York |
| MassMutual Federal Credit Union | Massachusetts |
| Masters, Mates & Pilots Federal Credit Union | Maryland |
| Matadors Community Credit Union | California |
| Matagorda County Credit Union | Texas |
| Matanuska Valley Federal Credit Union | Alaska |
| Materion Federal Credit Union | Ohio |
| Maternity B.V.M. Credit Union | Illinois |
| Matson Employees Federal Credit Union | California |
| Mattel Federal Credit Union | California |
| Mauch Chunk Trust Company | Pennsylvania |
| Maui County Federal Credit Union | Hawaii |
| Maui Federal Credit Union | Hawaii |
| Maui Teachers Federal Credit Union | Hawaii |
| Maumee Educators Federal Credit Union | Ohio |
| MAWC Credit Union | Missouri |
| MAX Credit Union | Alabama |
| Maxwell State Bank | Iowa |
| Maynard Savings Bank | Iowa |
| Mayo Employees Federal Credit Union | Minnesota |
| Mayville Savings Bank | Wisconsin |
| Mayville State Bank | Michigan |
| Mazon State Bank | Illinois |
| Mazuma Credit Union | Missouri |
| mBank | Michigan |
| MBank | Oregon |
| MB Financial Bank | Illinois |
| MBFT Federal Credit Union | Maryland |
| MBHS Federal Credit Union | Mississippi |
| MBL Bank | Louisiana |
| McAlester AAP Federal Credit Union | Oklahoma |
| McAlester Credit Union | Oklahoma |
| M C Bank & Trust Company | Louisiana |
| McBryde Federal Credit Union | Hawaii |
| McCabe Hamilton & Renny Federal Credit Union | Hawaii |
| McClain Bank | Oklahoma |
| McClatchy Employees Credit Union | California |
| McClave State Bank | Colorado |
| McComb Federal Credit Union | Mississippi |
| McCone County Federal Credit Union | Montana |
| McCook National Bank | Nebraska |
| McCoy Federal Credit Union | Florida |
| McCurtain County National Bank | Oklahoma |
| McDonald Community Federal Credit Union | Ohio |
| McDowell CornerStone Credit Union | North Carolina |
| McDowell County Federal Credit Union | West Virginia |
| McFarland State Bank | Wisconsin |
| McGehee Bank | Arkansas |
| McGraw Hill Federal Credit Union | New Jersey |
| McHenry County Federal Credit Union | Illinois |
| McHenry Savings Bank | Illinois |
| McIntosh Chemical Federal Credit Union | Alabama |
| McIntosh County Bank | North Dakota |
| McKeesport Area Public School Employees Federal Credit Union | Pennsylvania |
| McKeesport Bell Federal Credit Union | Pennsylvania |
| McKeesport Congregational Federal Credit Union | Pennsylvania |
| McKenzie Banking Company Foundation Bank | Tennessee |
| McKenzie Valley Federal Credit Union | Oregon |
| McKesson Employees Federal Credit Union | California |
| McKesson Federal Credit Union | Connecticut |
| McLennan County Employee Federal Credit Union | Texas |
| M&C Menlo Park Federal Credit Union | New Jersey |
| McMillen Master Credit Union | Illinois |
| McMurrey Federal Credit Union | Texas |
| McNairy County Employees Credit Union | Tennessee |
| MCNB Banks | West Virginia |
| McNeese Federal Credit Union | Louisiana |
| McPherson Community Federal Credit Union | Nebraska |
| McPherson Co-op Credit Union | Kansas |
| MCT Federal Credit Union | New York |