MSI
- Italian Social Movement
- List of mine warfare vessels of the United States Navy
- MSI Barcode
- MSI Reproductive Choices
- MSI protocol
- Macedonian Scientific Institute
- Magnetic source imaging
- Maison du Sport International
- Maritime safety information
- Marketing Science Institute
- Mass sociogenic illness
- Mass spectrometry imaging
- Media Sport Investment
- Medical Service Insurance
- Medium scale integration
- Message Signaled Interrupts
- Micro-Star International
- Microsatellite instability
- Mid-Season Invitational
- Midwest Scientific
- Millennium Science Initiative
- Mindless Self Indulgence
- Ministry of Science and Innovation (New Zealand)
- Minority-serving institution
- Morgan Stanley
- Motorola Solutions
- Movie Star (company)
- Multispectral imaging
- Multistakeholder initiative
- Musculoskeletal injury
- Museum of Science and Industry (Chicago)
- Science and Industry Museum
- University of Minnesota Supercomputing Institute
- Windows Installer