1. Macrophthalmidae Dana 1851
2. Macropodidae Gray 1821
3. Macrouridae Bonaparte 1831
4. Mactridae Lamarck 1809
5. Maeridae Krapp-Schickel 2008
6. Magnoliaceae de Jussieu 1789
7. Majidae Samouelle 1819
8. Malacanthidae Poey 1861
9. Malagazziidae Bouillon 1984
10. Maldanidae Malmgren 1867
11. Malvaceae de Jussieu 1789
12. Mantidae Burmeister 1838
13. Marteiliidae Sprague 1979
14. Matutidae De Haan 1835
15. Megachasmidae L.R. Taylor, Compagno & Struhsaker 1983
16. Megachilidae Latreille 1802
17. Megalopidae Jordan & Gilbert 1883
18. Megascolecidae Rosa 1891
19. Megathyrididae Dall 1870
20. Melicertidae Agassiz 1862
21. Melitidae Bousfield 1973
22. Menoponidae Mjöberg 1910
23. Menyanthaceae Dumortier 1829
24. Mermithidae Braun 1883
25. Merulinidae Verrill 1865
26. Mesodesmatidae Gray 1840
27. Mesogammaridae Bousfield 1977
28. Mesoveliidae Douglas & Scott 1867
29. Metastrongylidae Leiper 1908
30. Micrabaciidae Vaughan 1905
31. Microdesmidae Regan 1912
32. Micropleuridae Baylis & Daubney 1926
33. Molgulidae Lacaze-Duthiers 1877
34. Miliamminidae Saidova 1981
35. Milleporidae Fleming 1828
36. Miridae Hahn 1831
37. Mithrodiidae Viguier 1878
38. Mitridae Swainson 1829
39. Moerisiidae Poche 1914
40. Molidae Bonaparte 1832
41. Molineidae Skrjabin & Schulz 1937
42. Monacanthidae Nardo 1842
43. Moniliformidae Van Cleave 1924
44. Monocentridae Gill 1859
45. Montastraeidae Yabe & Sugiyama 1941
46. Mopaliidae Dall 1889
47. Moraceae Gaudichaud-Beaupré 1835
48. Moridae Moreau 1881
49. Mugilidae G. Cuvier 1829
50. Mullidae Rafinesque 1815
51. Munnidae Sars 1897
52. Muraenesocidae Kaup 1859
53. Muraenidae Rafinesque 1810
54. Murchisonellidae Casey 1904
55. Muricidae Rafinesque 1815
56. Muridae Illiger 1811
57. Musaceae de Jussieu 1789
58. Mussidae Ortmann 1890
59. Mustelidae G. Fischer de Waldheim 1817
60. Mycalidae Lundbeck 1905
61. Myctophidae T.N. Gill 1893
62. Myicolidae Yamaguti 1936
63. Myidae Lamarck 1809
64. Myliobatidae Bonaparte 1838
65. Myocastoridae Ameghino 1902
66. Mysidae Haworth 1825
67. Mytilicolidae Bocquet & Stock 1957
68. Mytilidae Rafinesque 1815
69. Myxinidae Rafinesque 1815