Encyclopedias, Almanacs, Transcripts, and Maps
- Marine Corps, US
- Marine Ecology
- Marine Ecology and Biodiversity
- Marine Geology and Geophysics
- Marine Invertebrates
- Marine Mammals Protection Act (1972)
- Marine Pollution
- Marine Protected Areas
- Marine Protection, Research and Sanctuaries Act (1972)
- Marine Provinces
- Mariner program
- Mark of Ephesus
- Mark the Evangelist
- Market Imperfections
- Market Transformation
- Marshall, George Perkins (1801 – 1882) American Diplomat, Philologist, Conservationist, Politician, and Lawyer
- Marshall, Robert (1901 – 1939) American Wilderness Advocate
- Marsupial Mice and Cats, Tasmanian Devil (Dasyuridae)
- Martial Arts: An Overview
- Martial Arts: Chinese Martial Arts