| Missouri Registered City Clerk | Business |
| M R Consultants Corporation | Business |
| Missouri Regional Certification Committee | Business |
| Midwest Radical Culture Corridor (artist and activist coalition) | Community |
| Montana Raptor Conservation Center | Community |
| Memorial Road Church of Christ | Community |
| Media Research Club of Chicago | Community |
| Matt Ross Community Center | Community |
| Missouri Rural Crisis Center | Community |
| Multi-Rate Congestion Control (web multicast transmission protocol) | Computing |
| Mandurah Rod and Custom Club | General |
| Mazda Rotary Club Cyprus | General |
| Mackay Rod and Custom Club | General |
| Modesto Radio Control Club | General |
| Metastatic Renal Cell Carcinoma | General |
| Missouri River Correctional Center | General |
| Multi Role Combat Craft | General |
| Maritime Rescue Centre Contact | General |
| Maritime Rescue Centre Coordination | General |
| Multi Region Clock Capable | General |
| Multi-Reference Coupled Cluster | General |
| Movement Report Control Center | Governmental |
| Military Rape Crisis Center (Boston, MA; est. 2006) | Governmental |
| Maritime Rescue Co-ordination Centre | Governmental |
| Michigan Regional Council of Carpenters | Governmental |
| Mildura Rural City Council | Governmental |
| Medical Regulating Control Center | Medical |
| Medical Representatives Certification Commission | Medical |
| Método Rápido de Clasificación en Catástrofes (Spanish: Fast Method of Classification in Catastrophes; medical care) | Medical |
| Coto 47, Costa Rica | Regional |
| Midwestern Regional Climate Center | Regional |
| Midwest Regional Climate Center | Regional |
| Mission Regional Chamber of Commerce | Regional |
| Mumbai Regional Congress Committee | Regional |
