| MITS Innovation and Research centre | Academic & Science |
| Midlands Innovation and Research Centre | Academic & Science |
| Marine Information Research Center | Academic & Science |
| McMaster Immunology Research Centre | Academic & Science |
| Moving Image Research Collections | Academic & Science |
| Musical Instrument Reclamation Corporation | Business |
| Musical Instrument Repair Corporation | Business |
| Management Information and Resource Centre | Business |
| Missouri Interagency Recycling Committee | Community |
| Medical Imaging Resource Community | Community |
| Minnesota Intelligent Rural Communities | Community |
| Management Information Report Control | Computing |
| Microsoft Internet Relay Chat | Computing |
| Mass Information Retrieval Connection | General |
| Mississippi Instructional Resource Center | General |
| Missouri Instructional Resource Center | General |
| MSX Infra Red Controller | General |
| Medicaid Innovation and Reform Commission | General |
| Member of the Idle Rich Class | General |
| Michigan Immigrant Rights Center | Governmental |
| Military Intelligence Reserve Command | Governmental |
| Morgridge International Reading Center | International |
| Modified Internet Relay Chat | Internet |
| Macro Internet Relay Chat | Internet |
| My Internet Relay Chat | Internet |
| Messenger Internet Relay Chat | Internet |
| Multiuser Internet Relay Chat | Internet |
| Medical Image Resource Center | Medical |
| Medical Imaging Resource Center | Medical |
| Medical Imaging Research Center | Medical |
| Multiple Internet Relay Chat | Messaging |
| Mechanized Infantry Regiment Centre (india) | Military and Defence |
