| Oahe Federal Credit Union | South Dakota |
| Oahu Federal Credit Union | Hawaii |
| Oak Bank | Illinois |
| Oak Bank | Wisconsin |
| Oak Cliff Christian Federal Credit Union | Texas |
| Oak Creek Valley Bank | Nebraska |
| Oakdale Credit Union | Wisconsin |
| Oakdale State Bank | Illinois |
| Oak Farms Employees Credit Union | Texas |
| Oakland County Credit Union | Michigan |
| Oak Lawn Municipal Employees Credit Union | Illinois |
| Oak Point Employees Credit Union | Louisiana |
| Oakstar Bank | Missouri |
| Oak Trust Credit Union | Illinois |
| Oak Valley Community Bank | California |
| Oak View National Bank | Virginia |
| Oakworth Capital Bank | Alabama |
| OAS Staff Federal Credit Union | District of Columbia |
| O'Bannon Bank | Missouri |
| O Bee Credit Union | Washington |
| Ocala Community Credit Union | Florida |
| Ocean Bank | Florida |
| Ocean Communities Federal Credit Union | Maine |
| Ocean County Employees Federal Credit Union | New Jersey |
| Ocean Crest Federal Credit Union | California |
| OceanFirst Bank | New Jersey |
| Oceanside Christopher Federal Credit Union | New York |
| Ocean Spray Employees Federal Credit Union | Massachusetts |
| Ocnac #1 Federal Credit Union | New Jersey |
| Oconee Federal Savings and Loan Association | South Carolina |
| Oconee State Bank | Georgia |
| Odessa Employees Credit Union | Texas |
| Odin State Bank | Minnesota |
| ODJFS Federal Credit Union | Ohio |
| OF Toalston Federal Credit Union | West Virginia |
| Ohana Pacific Bank | Hawaii |
| Ohio Catholic Federal Credit Union | Ohio |
| Ohio County Public Schools Federal Credit Union | West Virginia |
| Ohio Healthcare Federal Credit Union | Ohio |
| Ohio Operating Engineers Federal Credit Union | Ohio |
| Ohio Teamsters Credit Union | Ohio |
| Ohio University Credit Union | Ohio |
| Ohio Valley Bank | Ohio |
| Ohio Valley Community Credit Union | Ohio |
| Ohio Valley Federal Credit Union | Ohio |
| Ohnward Bank & Trust | Iowa |
| Oil Country Federal Credit Union | Pennsylvania |
| Ojai Community Bank | California |
| Okaloosa County Teachers Federal Credit Union | Florida |
| Okey-Vernon First National Bank | Iowa |
| OK Federal Credit Union | Oklahoma |
| Oklahoma Bank and Trust | Oklahoma |
| Oklahoma Central Credit Union | Oklahoma |
| Oklahoma Educators Credit Union | Oklahoma |
| Oklahoma Employees Credit Union | Oklahoma |
| Oklahoma Federal Credit Union | Oklahoma |
| Oklahoma Heritage Bank | Oklahoma |
| Oklahoma State Bank | Oklahoma |
| Oklahoma State Bank | Oklahoma |
| Oklahoma State Bank | Oklahoma |
| OK Members First Federal Credit Union | Oklahoma |
| Oko Cal Federal Credit Union | New Jersey |
| Olathe Federal Credit Union | Colorado |
| Old Dominion National Bank | Virginia |
| Old Dominion University Credit Union | Virginia |
| Old Exchange National Bank | Illinois |
| Old Fort Banking Company | Ohio |
| Old Hickory Credit Union | Tennessee |
| Old Line Bank | Maryland |
| Old Mission Bank | Michigan |
| Old Missouri Bank | Missouri |
| Old National Bank | Indiana |
| Old Ocean Federal Credit Union | Texas |
| Old Plank Trail Community Bank | Illinois |
| Old Second National Bank | Illinois |
| Old South Federal Credit Union | Mississippi |
| Old Spanish Trail Credit Union | Louisiana |
| OldTown Bank | North Carolina |
| Old West Federal Credit Union | Oregon |
| Olean Area Federal Credit Union | New York |
| Olean Teachers' and Postal Federal Credit Union | New York |
| Olivet Baptist Credit Union | Tennessee |
| Olive View Employees Federal Credit Union | California |
| Olmsted National Bank | Minnesota |
| Olympia Credit Union | Washington |
| Olympia Federal Savings and Loan Association | Washington |
| Omaha Douglas Federal Credit Union | Nebraska |
| Omaha Federal Credit Union | Nebraska |
| Omaha Firefighters Credit Union | Nebraska |
| Omaha Police Federal Credit Union | Nebraska |
| Omaha Public Power District Employees Federal Credit Union | Nebraska |
| O.M.C. Employees Credit Union | Tennessee |
| Omega Federal Credit Union | Pennsylvania |
| OmniBank | Mississippi |
| Omni Community Credit Union | Michigan |
| O'Neal Credit Union | Alabama |
| One American Bank | South Dakota |
| One Bank & Trust | Arkansas |
| One Community Federal Credit Union | West Virginia |
| One Credit Union | Vermont |