Encyclopedias, Almanacs, Transcripts, and Maps
- Maximón
- Maximos the Confessor
- Maximum Permissible Concentration
- May beetle
- Maya Religion
- Mayan
- Mayer, Julius Robert (1814–1878)
- Mazarin, Jules, Cardinal
- Mazdakism
- Mbona
- McCartney, Sir Paul
- McCullin, Donald
- McHarg, Ian Lennox (1920 – 2001) Scottish Design Ecologist and Writer
- McKibben, Bill Ernest (1960 – ) American Environmentalist and Writer
- Me?ir
- Me?ir ben Barukh of Rothenburg
- Measurement and Sensing
- mechanical advantage
- Mechanical Transmission of Energy
- Mecoptera (Scorpionflies and Hangingflies)