B
- Bahaba taipingensis — Chinese bahaba
- Balaenoptera borealis — Coalfish Whale, Pollack Whale, Rudolphi's Rorqual, Sei Whale
- Balaenoptera musculus — Blue Whale, Sibbald's rorqual, Sulphur-bottom whale
- Balaenoptera physalus — Common Rorqual, Fin Whale, Fin-backed Whale, Finback, Finner, Herring Whale, Razorback
- Balantiocheilos melanopterus — Silver Shark
- Balantiopteryx infusca — Ecuadorian Sac-winged Bat
- Balebrevied Cinclodes
- Batagur baska — Batagur, Common Batagur, Four-toed Terrapin, River Terrapin, Batagur Malais, Galápago Batagur
- Bathanalia howesi
- Batrachophrynus brachydactylus
- Batrachophrynus macrostomus — Lake Junin Frog
- Batrachoseps campi — Inyo Mountains Salamander
- Batrachuperus cochranae
- Batrachuperus gorganensis — Gorgan Salamander
- Batrachuperus londongensis — Longdong Stream Salamander
- Batrachuperus mustersi — Afghani Brook Salamander
- Beatragus hunteri — Hirola, Hunter's Antelope, Hunter's hartebeest
- Beddomeia capensis
- Beddomeia fallax
- Beddomeia minima
- Bedotia sp. nov. 'Manombo'
- Bedotia sp. nov. 'Sambava'
- Bedotia sp. nov. 'Vevembe'
- Bedotia tricolor
- Belgrandiella austriana
- Belgrandiella ganslmayri
- Belgrandiella mimula
- Belgrandiella parreyssi
- Belgrandiella pelerei
- Belgrandiella styriaca
- Belgrandiella wawrai
- Bellamya constricta
- Bellamya contracta
- Bellamya crawshayi
- Bellamya leopoldvillensis
- Bellamya liberiana
- Bellamya monardi
- Bellamya mweruensis
- Bellamya pagodiformis
- Bellamya phthinotropis
- Bellamya robertsoni
- Bellamya rubicunda
- Bellamya trochearis
- Bermudalana aruboides
- Bermudamysis speluncola
- Betta livida
- Betta miniopinna
- Betta persephone
- Betta spilotogena
- Bettongia tropica — Northern Bettong
- Biomphalaria barthi
- Bison bonasus — European Bison, Wisent
- Biswamoyopterus biswasi — Namdapha Flying Squirrel
- Bogidiella bermudensis
- Bokermannohyla izecksohni
- Bolitoglossa alvaradoi
- Bolitoglossa capitana
- Bolitoglossa carri
- Bolitoglossa celaque
- Bolitoglossa compacta
- Bolitoglossa conanti
- Bolitoglossa decora
- Bolitoglossa diaphora
- Bolitoglossa dunni
- Bolitoglossa engelhardti
- Bolitoglossa flavimembris
- Bolitoglossa franklini
- Bolitoglossa heiroreias — Holy-mountain Salamander
- Bolitoglossa jacksoni
- Bolitoglossa longissima
- Bolitoglossa magnifica — Magnificent Web-footed Salamander
- Bolitoglossa marmorea
- Bolitoglossa meliana
- Bolitoglossa minutula
- Bolitoglossa odonnelli
- Bolitoglossa oresbia
- Bolitoglossa pandi
- Bolitoglossa pesrubra
- Bolitoglossa porrasorum
- Bolitoglossa riletti
- Bolitoglossa salvinii
- Bolitoglossa sooyorum
- Bolitoglossa spongai
- Bolitoglossa stuarti
- Bolitoglossa subpalmata
- Bolitoglossa synoria
- Boninagrion ezoin
- Boninena callistoderma
- Boninena hiraseana
- Boninena ogasawarae
- Boninthemis insularis
- Boophis williamsi
- Bos javanicus — Banteng, Tembadau
- Bos sauveli — Grey Ox, Kouprey
- Bostrychia bocagei — Dwarf Olive Ibis
- Botaurus poiciloptilus — Australasian Bittern
- Bothriembryon perobesus
- Bothriembryon praecelcus
- Bothrops alcatraz — Alcatrazes Lancehead
- Bothrops insularis — Golden Lancehead, Queimada Island Bothrops
- Botia sidthimunki
- Boucardicus carylae
- Boucardicus culminans
- Boucardicus curvifolius
- Boucardicus delicatus
- Boucardicus divei
- Boucardicus esetrae
- Boucardicus fidimananai
- Boucardicus fortistriatus
- Boucardicus magnilobatus
- Boucardicus mahermanae
- Boucardicus randalanai
- Boucardicus simplex
- Boucardicus victorhernandezi
- Boulengerula niedeni
- Brachionichthys hirsutus — Spotted handfish
- Brachylophus fasciatus — Fiji Banded Iguana, South Pacific Banded Iguana
- Brachylophus vitiensis — Fiji Crested Iguana
- Brachyramphus brevirostris — Kittlitz's Murrelet
- Brachyramphus marmoratus — Marbled Murrelet
- Brachyteles arachnoides — Muriqui, Southern Muriqui, Woolly Spider Monkey
- Brachyteles hypoxanthus — Northern Muriqui, Muriqui
- Bradypodion setaroi — Setarolondongensis — Longdong Stream Salamander
- Brychius hungerfordi — Hungerford's crawling water beetle
- Batrachuperus mustersi — Afghani Brook Salamander
- Beatragus hunteri — Hirola, Hunter's Antelope, Hunter's hartebeest
- Beddomeia capensis
- Beddomeia fallax
- Beddomeia minima
- Bedotia sp. nov. 'Manombo'
- Bedotia sp. nov. 'Sambava'
- Bedotia sp. nov. 'Vevembe'
- Bedotia tricolor
- Belgrandiella austriana
- Belgrandiella ganslmayri
- Belgrandiella mimula
- Belgrandiella parreyssi
- Belgrandiella pelerei
- Belgrandiella styriaca
- Belgrandiella wawrai
- Bellamya constricta
- Bellamya contracta
- Bellamya crawshayi
- Bellamya leopoldvillensis
- Bellamya liberiana
- Bellamya monardi
- Bellamya mweruensis
- Bellamya pagodiformis
- Bellamya phthinotropis
- Bellamuffalo
- Bubalus depressicornis — Anoa, Lowland Anoa
- Bubalus mindorensis — Tamaraw, Tamarou, Tamarau
- Bubalus quarlesi — Mountain Anoa
- Bufo amabilis
- Bufo amatolicus — Amatola Toad
- Bufo beddomii
- Bufo brauni
- Bufo caeruleostictus
- Bufo californicus — Arroyo toad
- Bufo canorus — Yosemite Toad
- Bufo cataulaciceps — Cuban Pine Toad
- Bufo cavifrons — Mountain Toad
- Bufo chavin
- Bufo claviger
- Bufo cristatus — Large-crested Toad
- Bufo djohongensis
- Bufo fastidiosus
- Bufo fluviaticus — Hispaniolan Crestless Toad
- Bufo fractus — Eastern Crested Toad
- Bufo gallardoi
- Bufo gemmifer — Jeweled Toad
- Bufo holdridgei
- Bufo houstonensis — Houston Toad
- Bufo ibarrai
- Bufo inyangae — Inyanga Toad
- Bufo kotagamai
- Bufo koynayensis
- Bufo kumquat
- Bufo lemur — Puerto Rican Crested Toad, Puerto Rican Toad
- Bufo leucomyos
- Bufo longinasus — Cuban Long-nosed Toad
- Bufo nelsoni — Amargosa Toad
- Bufo nesiotes
- Bufo noellerti
- Bufo pantherinus — Western Leopard Toad
- Bufo peripatetes
- Bufo perplexus
- Bufo sclerocephalus
- Bufo spiculatus
- Bufo sumatranus
- Bufo tacanensis
- Bufo taiensis
- Bufo tutelarius
- Bufo villiersi
- Bufoides meghalayanus
- Bulimulus achatellinus
- Bulimulus adelphus
- Bulimulus adserseni
- Bulimulus chemitzioides
- Bulimulus cinerarius
- Bulimulus cucullinus
- Bulimulus curtus
- Bulimulus deridderi
- Bulimulus duncanus
- Bulimulus eos
- Bulimulus eschariferus
- Bulimulus galapaganus
- Bulimulus habeli
- Bulimulus hirsutus
- Bulimulus indefatigabilis
- Bulimulus jacobi
- Bulimulus lycodus
- Bulimulus nux
- Bulimulus ochsneri
- Bulimulus olla
- Bulimulus perspectivus
- Bulimulus planospira
- Bulimulus reibischi
- Bulimulus rugulosus
- Bulimulus saeronius
- Bulimulus sculpturatus
- Bulimulus sp. nov. 'josevillani'
- Bulimulus sp. nov. 'krameri'
- Bulimulus sp. nov. 'nilsodhneri'
- Bulimulus sp. nov. 'tuideroyi'
- Bulimulus sp. nov. 'vanmoli'
- Bulimulus tanneri
- Bulimulus wolfi
- Bulinus succinoides
- Bunolagus monticularis — Bushman Hare, Riverine Rabbit
- Bunomys coelestis — Heavenly Hill Rat
- Bunomys prolatus — Long-headed Hill Rat
- Bunopithecus hoolock — Hoolock Gibbon, Hoolock
- Burmagomphus sivalikensis
- Burramys parvus — Broom's Pygmy-possum, Burramys, Mountain Pygmy Possum
- Buteo ridgwayi — Ridgway's Hawk
- Buthraupis aureodorsalis — Golden-backed Mountain-tanager
- Bythinella bicarinata
- Bythiospeum cisterciensorum
- Bythiospeum geyeri
- Bythiospeum noricum
- Bythiospeum pfeifferi
- Bythiospeum reisalpense
- Bythiospeum tschapecki
Read more about this topic: IUCN Red List Endangered Animal Species