M
- Macaca maurus — Celebes Macaque, Moor Macaque
- Macaca nigra — Celebes Black Macaque, Celebes Crested Macaque, Celebes Macaque, Crested Black Macaque, Gorontalo Macaque, Sulawesi Macaque
- Macaca pagensis — Mentawai Macaque
- Macaca silenus — Lion-tailed Macaque, Liontail Macaque, Wanderoo
- Maccullochella ikei — Clarence River Cod, Eastern Freshwater Cod
- Maccullochella macquariensis — Trout Cod
- Maccullochella peelii — Mary River Cod
- Macroagelaius subalaris — Mountain Grackle
- Macrocephalon maleo — Maleo
- Macromia flinti
- Macromia kubokaiya
- Macromidia ishidai
- Macronyx sharpei — Sharpe's Longclaw
- Macroperipatus insularis
- Macropleurodus bicolor
- Macrosphenus pulitzeri — Pulitzer's Longbill
- Macrotarsomys ingens — Greater Big-footed Mouse
- Macrovipera schweizeri — Cyclades blunt-nosed viper, Milos viper
- Macruromys elegans — Lesser Small-toothed Rat, Western Small-toothed Rat
- Macruromys major — Eastern Small-toothed Rat
- Madanga ruficollis — Rufous-throated White-eye
- Madecassophryne truebae
- Mahatha helaya
- Mahatha iora
- Mahatha lacuna
- Mahatha regina
- Makalata occasius
- Malaconotus alius — Uluguru Bush-shrike
- Malaconotus kupeensis — Mount Kupe Bush-shrike
- Malimbus ballmanni — Gola Malimbe
- Malimbus ibadanensis — Ibadan Malimbe
- Mallomys gunung — Alpine Woolly Rat
- Mandibularca resinus — Bagangan
- Mandrillus leucophaeus — Drill
- Mannophryne caquetio
- Mannophryne collaris
- Mannophryne lamarcai
- Mannophryne neblina
- Mannophryne olmonae — Bloody Bay Poison Frog
- Mannophryne riveroi
- Mannophryne yustizi
- Manorina melanotis — Black-eared Miner
- Manouria emys — Asian Forest Tortoise, Asian Giant Tortoise, Black Giant Tortoise, Burmese Brown Tortoise, Burmese Mountain Tortoise, Six-legged Tortoise
- Mantella aurantiaca — Golden Frog, Golden Mantella
- Mantella bernhardi — Bernhard's Mantella
- Mantella cowanii — Cowan's Mantella
- Mantella crocea — Yellow Mantella
- Mantella expectata — Blue-legged Mantella
- Mantella milotympanum — Black-eared Mantella
- Mantella viridis — Green Mantella
- Mantidactylus brunae
- Mantidactylus corvus
- Mantidactylus guibei
- Mantidactylus horridus
- Mantidactylus madecassus
- Mantidactylus microtis
- Mantidactylus microtympanum
- Mantidactylus pauliani
- Mantidactylus silvanus
- Mantidactylus webbi
- Marcusenius victoriae — Victoria stonebasher
- Margaritifera auricularia — Spengler's freshwater mussel
- Margaritifera hembeli — Louisiana pearlshell
- Margaritifera margaritifera — Freshwater Pearl Mussel
- Margaritifera marrianae — Alabama pearl shell
- Marmosa andersoni — Anderson's Mouse Opossum
- Marmosa xerophila — Dryland Mouse Opossum
- Marmosops cracens — Slim-faced Slender Mouse Opossum
- Marmosops handleyi — Handley's Slender Mouse Opossum
- Marmota vancouverensis — Vancouver Island Marmot, Vancouver Marmot
- Martelia tanganyicensis
- Mathewsoconcha belli
- Mauremys annamensis — Annam Leaf Turtle, Vietnamese Pond Turtle
- Mauremys mutica
- Mautodontha boraborensis
- Mautodontha ceuthma
- Maxomys alticola — Mountain Spiny Rat
- Maxomys baeodon
- Maxomys wattsi — Watts's Spiny Rat
- Mbipia lutea
- Mecistogaster pronoti — Atlantic Helicopter
- Medionidus acutissimus — Alabama moccasinshell
- Medionidus parvulus — Coosa moccasinshell
- Medionidus penicillatus — Gulf moccasinshell
- Medionidus simpsonianus — Ochlockonee moccasinshell
- Medionidus walkeri
- Megadyptes antipodes — Yellow-eyed Penguin
- Megalagrion leptodemas — Crimson Hawaiian Damselfly
- Megalagrion molokaiense — Molokai Damselfly
- Megalagrion nesiotes — Flying Earwig Hawaiian Damselfly
- Megalobulimus fragilion
- Megalobulimus grandis
- Megalobulimus lopesi
- Megalobulimus parafragilior
- Megalobulimus proclivis
- Megapodius laperouse — Micronesian Megapode
- Megapodius pritchardii — Polynesian Megapode
- Megastomatohyla mixe
- Megastomatohyla mixomaculata
- Megastomatohyla nubicola
- Megastomatohyla pellita
- Megophrys ligayae — Palawan Horned Frog
- Meladema imbricata
- Melamprosops phaeosoma — Po'o-uli
- Melanobatrachus indicus — Black Microhylid
- Melanophryniscus devincenzii
- Melanospiza richardsoni — St Lucia Black Finch
- Melanotaenia boesemani — Boeseman's rainbowfish
- Melasmothrix naso — Sulawesian Shrew Rat
- Melomys rubicola — Bramble Cay Mosaic-tailed Rat
- Mergus octosetaceus — Brazilian Merganser
- Mergus squamatus — Scaly-sided Merganser
- Meridolum corneovirens
- Meriones arimalius — Arabian Jird
- Meriones chengi — Cheng's Jird
- Meriones dahli — Dahl's Jird
- Meriones sacramenti — Buxton's Jird
- Meriones zarudnyi — Zarundny's Jird
- Merulaxis stresemanni — Stresemann's Bristlefront
- Mesocapromys angelcabrerai — Cabrera's Hutia
- Mesocapromys auritus — Eared Hutia, Large-eared Hutia
- Mesocapromys nanus — Dwarf Hutia
- Mesocapromys sanfelipensis — Little Earth Hutia, San Felipe Hutia
- Mesocricetus auratus — Golden Hamster
- Mesodon clenchi — Clench's middle-toothed land snail, Mission Creek Oregonian
- Mesonerilla prospera
- Metabolus rugensis — Chuuk Monarch
- Metacnemis valida — Kubusi Stream Damsel
- Metallura baroni — Violet-throated Metaltail
- Metallura iracunda — Perijá Metaltail
- Mexistenasellus coahuila
- Micrarionta feralis — Fraternal snail, San Nicolas Island snail
- Micrixalus gadgili
- Micrixalus kottigeharensis
- Microbatrachella capensis — Micro Frog
- Microcebus myoxinus
- Microcebus ravelobensis — Golden-brown Mouse Lemur
- Microgale jenkinsae
- Microgale nasoloi — Nasolo's Shrew Tenrec
- Microgomphus wijaya
- Microhyla karunaratnei
- Microhyla sholigari
- Microhyla zeylanica
- Micromacromia miraculosa
- Microneura caligata — Blue-and-orange Threadtail
- Micropotamogale lamottei — Nimba Otter Shrew, Pygmy Otter-shrew
- Microstrophia modesta
- Microtus evoronensis — Evorsk Vole
- Microtus kermanensis — Baluchistan Vole
- Microtus mujanensis — Muisk Vole
- Micryletta steinegeri
- Mictocaris halope
- Millardia kondana — Kondana Soft-furred Rat
- Mimus graysoni — Socorro Mockingbird
- Minervarya sahyadris
- Miniopterus robustior — Loyalty Bent-winged Bat
- Mirafra ashi — Ash's Lark
- Mixophyes fleayi — Fleay's Barred Frog, Fleay's Frog
- Mixophyes iteratus — Giant Barred Frog, Giant Barred River-frog, Giant Barred-frog, Southern Barred Frog
- Moapa coriacea — Moapa dace
- Mobula mobular — Devil fish
- Mogera etigo — Echigo Mole
- Mogera tokudae — Sado Mole, Tokuda's Mole
- Mohoua ochrocephala — Yellowhead
- Monachus monachus — Mediterranean Monk Seal
- Monachus schauinslandi — Hawaiian Monk Seal
- Monarcha boanensis — Black-chinned Monarch
- Monarcha brehmii — Biak Monarch
- Monarcha everetti — White-tipped Monarch
- Monarcha sacerdotum — Flores Monarch
- Monodelphis kunsi — Pygmy Short-tailed Opossum
- Monolistra bolei
- Monolistra spinosissima
- Monticola erythronotus — Amber Mountain Rock-thrush
- Montivipera bornmuelleri — Lebanon Viper
- Mormopterus phrudus — Incan Little Mastiff Bat
- Mouldingia orientalis
- Mungotictis decemlineata — Malagasy Narrow-striped Mongoose, Narrow-striped Mongoose
- Muriculus imberbis — Ethiopian Striped Mouse, Striped-back Mouse
- Murina grisea — Peter's Tube-nosed Bat
- Murina tenebrosa — Gloomy Tube-nosed Bat
- Murina ussuriensis — Ussuri Tube-nosed Bat
- Mus famulus — Servant Mouse
- Mustela felipei — Colombian Weasel
- Mustela lutreola — European Mink
- Mustela lutreolina — Indonesian Mountain Weasel
- Mustelus fasciatus — Striped dogfish, Striped smooth-hound
- Mustelus schmitti — Narrownose smooth-hound
- Myadestes lanaiensis — Oloma'o
- Myadestes palmeri — Puaiohi
- Myaka myaka
- Myioborus pariae — Paria Whitestart
- Myiotheretes pernix — Santa Marta Bush-tyrant
- Myliobatis hamlyni — Purple Eagle Ray
- Myomimus setzeri — Setzer's Mouse-tailed Dormouse
- Myonycteris brachycephala — Sao Tomé Collared Fruit Bat
- Myophonus blighi — Sri Lanka Whistling-thrush
- Myosorex eisentrauti — Eisentraut's Mouse Shrew
- Myosorex kihaulei
- Myosorex okuensis — Oku Mouse Shrew
- Myosorex rumpii — Rumpi Mouse Shrew
- Myotis cobanensis — Guatemalan Myotis
- Myotis findleyi — Findley's Myotis
- Myotis grisescens — Gray Myotis, Grey Bat
- Myotis ozensis — Honshū Myotis
- Myotis planiceps — Flat-headed Myotis
- Myotis pruinosus — Frosted Myotis
- Myotis schaubi — Schaub's Myotis
- Myotis sodalis — Indiana Bat, Social Bat
- Myotis stalkeri — Kei Myotis
- Myrmeciza ruficauda — Scalloped Antbird
- Myrmotherula fluminensis — Rio De Janeiro Antwren
- Myrmotherula snowi — Alagoas Antwren
- Mysateles garridoi — Garrido's Hutia
- Mystromys albicaudatus — White-tailed Mouse, White-tailed Rat
Read more about this topic: IUCN Red List Endangered Animal Species