| Abbreviation | Definition |
|---|---|
| MHAA | Mid Hudson Astronomy Association |
| MHGL | Mexican Hat Gravitational Lens |
| MI | Maximum Influence |
| MIISE | Mid Infrared Imager and Spectragraph |
| MIP | Moon Impact Probe |
| MJ | Mass of Jupiter |
| MKN | Markarian (celestial object) |
| MLPS | Mid-Latitude Plasma Structuring |
| MLRS | McDonald Laser Ranging Station |
| MLY | Mega Light Year |
| MM | Missing Mass |
| MMA | Milli Modulation Amplitude |
| MMT | Multiple Mirror Telescope |
| MMTF | Maryland-Magellan Tunable Filter |
| MMTO | Multiple Mirror Telescope Observatory |
| MNRAS | Monthly Notices of the Royal Astronomical Society |
| MO | Monotonic Convention |
| MOE | Moon Of Earth |
| MOM | Mars Orbiter Mission |
| MOST | Microvariability Oscillations of STars |