• Maccoyella Etheridge, 1892 †
• Macoyella Etheridge, 1902 † (unaccepted)
• Marcella Dognin, 1914
• Marcetella Sventenius, 1948 accepted as Bencomia Webb & Berthelot, 1842
• Marcorella (Necker ex G. Don) Rafinesque, 1838 (uncertain)
• Marcouella Shaw, 1966 † (uncertain)
• Marcusella Westblad, 1953
• Mardoella Bell, 1906 accepted as Mardoell Danielssen, 1890 accepted as Epizoanthus Gray, 1867
• Maricopella Roth, 1996
• Mariomella Faúndez & Rider, 2019
• Marionella Bancroft, 1928 † accepted as Multicostella Schuchert & Cooper, 1931 † [Family: Plaesiomyidae]
• Marionella Cobb, 1922 accepted as Eurystomina Filipjev, 1921 [Family: Enchelidiidae]
• Marionella F.S. Wagner, 1954 [Family: Delesseriaceae]
• Marocella Geyer, 1986 † (uncertain)
• Maronella M. Steiner, 1959 accepted as Biatorella G. De Notaris, 1846
• Martorella Caldwell in Caldwell & Martorell, 1951
• Marzoella Chiocchini & Mancinelli, 2000 † (uncertain)
• Maslovella H. Tappan & A.R. Loeblich Jr., 1966 † accepted as Watznaueria P. Reinhardt, 1964 † [Family: Watznaueriaceae]
• Maslovella R.B. Samoilova, 1986 † accepted as Sycidium G. Sandberger, 1849 † [Family: Sycidiaceae]