| Abbreviation | Definition |
|---|---|
| MOST | Molonglo Observatory Synthesis Telescope |
| MP | Massive Protostar |
| MPAS | Mornington Peninsula Astronomical Society |
| MPEC | Minor Planet Electronic Circular |
| MPH | Miles Per Hour |
| MPIA | Max Planck Institute for Astronomy |
| MPPG | Mars Program Planning Group |
| MR | Measurement of Red |
| MR | Moonlight Rising |
| MRK | Markarian (celestial object) |
| MRO | Mars Reconnaissance Orbiter |
| MS | Main Sequence |
| MS | Meteor Scatter |
| MS | Millions of Stars |
| MS | Morning Star |
| MSAS | Mansfield and Sutton Astronomical Society |
| MSAS | Mexborough and Swinton Astronomical Society |
| MSFN | Manned Space Flight Network |
| MSO | Mount Stromlo Observatory |
| MSP | Millisecond Pulsar |