- Malacosporea
- Malacovalvulida Canning et al., 2000
- Meglitschia Kovaljova, 1988
- Multivalvulida
- Mytraspora Fujita, 1912
- Myxidiidae Thélohan, 1892
- Myxidium Buetschli, 1882
- Myxobilatus Davis, 1944
- Myxobolidae Thélohan, 1892
- Myxobolus Bütschli, 1882
- Myxoproteus Doflein, 1898
- Myxosporea