Here is a list of all species ever known to Star Trek. I have over 700 Species on this page.
A's
Acamarian
Akaali
Akritiri
Aksani
Al-Leyan
Alcyones
Aldean
Aldebaran Shellmouth
Aldebarran Serpent
Aldeberan mud leech
Algolians
Algorian Mammoth
Allasomorph
Alsuran
Altarian marsupial
Altoran
Alvanian Cave Sloth
Alvanian Spine Mite
Alvera trees
Alverian Dung Beetle
Amoeba
Amphibian
Anaconda
Anaphasic life forms
Andarians
Andorian Amoeba
Andorians
Angelian
Angosian
Ankari
Annari
Antarans
Antarians
Antedean
Antican
Apollo
Arachnid
Arbazan
Arbazon Vulture
Arcadian
Arcturian
Ardanan
Argalan
Argellians
Argosian
Argrathi
Arkarian
Arkarian Water Fowl
Arkenite
Arkonians
Armus
Arritheans
Atrean
Australopithecine
Axanar
B's
B'omar
B'Saari
Ba'ku
Ba'Neth
Bacillus Spray
Bajoran Shrimp
Bajorans
Balduk
Bamboo
Bandi
Banean
Baneriam Hawk
Bardakian Pronghorn Moose
Bardeezan
Barkonian
Barolians
Barrowbug
Barzan
Bat
Beauregard
Belzoidian Flea
Benkaran
Benthan
Benzites
Berellians
Berserker Cat
Beta Runner Cloud
Beta XII-A Entity
Betazoids
Bilanan
Bluehorns
Bok-rat
Bolians
Boraalan
Boranian
Bore worms
Borg
Borgia Plant
Boslic
Botha
Bre'el
Breen
Brekkian
Brenari
Bringloidi
Briori
Brunali
Bunny Rabbit
Buranian
Bynars
Byzallian
Byzatium
C's
Caatati
Cairn
Caitian
Calamaraine
Caldonian
Caldorian Eel
Calrissian Chameleon
Camorites
Canary
Capellan
Cardassians
Caretaker
Carlotti
Carnivorous Rastipod
Cat
Cave-Rat
Ceti Eel
Chalnoth
Chameloid
Chessu
Chrysallians
Circassian Cat
Coalescent organism
Companion
Conciousness Parasite
Coridans
Corvallen
Corvan Gilvos
Cove Palm
Cravic
Crystalline Entity
Crystilia
Cyperon Cactus
Cypriprdium
Cytherian
D's
D'Arsay
Dachlyds
Dal'Rok
Daliwakan
Dalvin Hissing Beetle
Debrune
Degebian Mountain Goat
Dekendi
Deltan
Demerians
Demons
Denebian Slime Devil
Denebians
Denevan Neural Parasite
Denobulan Lemur
Denobulans
Devidian
Devore
Digger
Dikironium Cloud Creature
Dinaali
Diomedian Scarlet Moss
Distortion ring Being
Dog
Dolphin
Doosodarians
Doptarians
Dosi
Douwd
Drabidium Calimus
Draco Lizards
Dralian
Drathan Puppy Lig
Draxxan cloud viper
Drayans
Drayjin
Dream Species
Drella
Dreman
Druoda
Dryworm
E's
Earthworm
Edo god
Edosian slugs
Eel-birds
Ekosians
El-Aurians
Elasian
Elaysian
Ellora
Emergent life form
Eminians
Enaran
Ennis / Nol-Ennis
Enolians
Entabans
Entharan
Eryops
Eska
Etanian Order
Evora
Excalbian
Exocomp
F's
Fabrini
Fargan
Farn
Farpoint Station
Felaran Rose
Ferengi
Fire Ants
Fire Beast of Sullus
Fire Snakes
Fire wolves
Flitter Bird
Folnar Jewel Plant
Founders
Frunalian
G's
Gagh
Galipotans
Gallamite
Gamelan
Garanian Bolites
Garden snake
Garenor
Garili Tree
Garlanic Tree
Garren
Gatherers
Gavarian
Gideons
Glob fly
Golanans
Gomtuu
Gorgan
Gorn
Gorokian Midwife Toad
Grazerite
Gree
Grisella
Gulgallian Rat
Gunji Jackdaw
H's
Haakonians
Hadrosaur
Halanans
Haliian
Halkans
Hanonian Land Eel
Hara cat
Haradin
Harkonian
Havenite
Hazari
Hekaran
Hierarchy, The
Hill People
Hirogen
Horta
Humans
Humpback Whale
humuhumunukunukuapua'a
Hunters
Hupyrians
Hur'q
Husnock
I's
Ice Bores
Iconians
Idanian
Iguana
Ikaaran
Ilari
Ilidarians
Illyrians
Imhotep
Immunocytic Gel Worms
Inheritors
Interphasic Organisms
Iothra
Iotians
Isis
Ithenites
Iyaaran
J's
J'naii
Jarada
Jem'Hadar
Joranian Ostrich
K's
Kadi
Kaelon
Kalandans
Kantareans
Karemma
Kartelans
Kataanians
Kavarian tiger-bat
Kazleti
Kazon
Kellerun
Kelvans
Kerelian
Kes
Kesat
Kesprytt
Khefkan
Kinbori
Klabnian Eel
Klaestron
Klingons
Kobali
Kobheerians
Kobliad
Kohl
Kohms
Koinonian
Kolar Beast
Kolarin
Kolhari
Komar
Komarians
Kostolain
Kovaalans
Kradin
Krallinian Eel
Kraylor
Kreetassian
Krellans
Krenim
Kressari
Kriosians
Kryonian Tiger
Ktarians
Kyrians
L's
L-S VI Life-form
Lapling
Lavaflies
LB10445
Leaf Miners
Ledosian
Legarans
Lemur
Lenarians
Lethean
Leyrons
Ligonian
Ligorian Mastodon
Lissepians
Lokirrim
Loon
Loque'eque
Lothra
Lumerian
Lurians
Lurillian
Lycosa Tarantula
Lynars
Lysians
Lyssarian desevae
Lyssarians
Lytasians
M's
M'klexa
M-113 Creature
Macrovirus
Makers
Malcorian
Malkoth
Malon
Malosian
Malurian
Manchovites
Maple Trees
Mari
Marijne VII Beings
Markoffian Sea Lizard
Marlonian
Mathenites
Mawasi
Mazarite
Medusan
Megaptera Novaeangliae
Megarite
Melkotian
Mellitus
Melvaran mud flea
Memory Virus
Menk
Menthar
Meridians
Metalic Microbes
Metrones
Microbiotic Colony
Microbrain
Microvirus
Mikhal Traveller
Mikulaks
Minnobia
Mintakans
Miradorn
Mislan
Mizarian
Mokra
Monean
Mordanian
Mordian Butterfly
Morg/Eymorg
Moriarty
Moropa
Mugato
Muktok Plant
Muse
Mylean
N's
Nagilum
Nakan
Nanites
Napean
Nasari
Nassordin
Nasturtium
Nausicaans
Nechani
Neethian Catfish
Neo-Roman
Neuralian
Nexian tapeworm
Nezu
Night Beings
Nihydron
Nitrium Metal Parasites
Noophians
Norcadians
Norpin Falcon
Nucleogenic Cloud Being
Nucleogenic Lifeform
Numiri
Nuu'bari
Nuvian
Nyberrite Alliance
Nygean
Nyrian
O's
Ocampa
