List of fictional alien species: D

Name	Source	Type
Daemonites	Wildstorm
Daimons	Sailor Moon	Purplish-skinned amorphous monsters that are forms of life native to the Tau Ceti Star System, who act as minions of the main antagonists of the third arc, the Death Busters.
	Marvel Comics	Humanoid
Daktaklakpak	Star Control 3
Daleks	Doctor Who	Mutated squid-like lifeforms inside tank-like war machines. Xenophobic and power-hungry, they have repeatedly threatened the universe and are the most recurring enemies of the Doctor.
	Marvel Comics	Humanoid
Dantari	Star Wars
Darjakr'Ul	Utopia
Dark Eldar	Warhammer 40,000	Humanoid pirates dedicated to sadism and depravity.
Darloks	Master of Orion
	Traveller RPG
	Haegemonia: Legions of Iron
Daxamites	DC Comics	Humanoid
Decapodian	Futurama	Lobster people. Bright red, with tentacles over their mouths. When they mate, they die horribly.
Decepticon	Transformers	Faction of Cybertronians who are opposed to the Autobots. Ill intent for human race.
DearS	DearS	Humanoid
Deep Ones	H. P. Lovecraft	Fish-like humanoids who serve and worship the Great Old Ones known as Father Dagon and Mother Hydra.
Deep Ones	X-COM: Terror from the Deep
Defiance	Genesis Rising	band of many different races
	The History of the Galaxy series
Deltans	Star Trek	Humanoid
Delvians	Farscape	Humanoid - Similar to humans in appearance, but evolved from plants. Blue, bald, sensitive to sunlight, procreate through air-borne spores.
Demiurg	Warhammer 40,000
		Humanoid
Denebians	Star Wars
	Keith Laumer's Bolo series	Arachnoids
Denobulans	Star Trek	Humanoid
	Farscape	Gastropod / Slug-like. Symbiotic relationship, used for dental hygiene purposes: This small animal thoroughly cleans the teeth of the user in a short amount of time.
Dentrassis	The Hitchhiker's Guide to the Galaxy	Dedicated chefs who "don't give a wet slap about anything else".
Deoxys	Pokémon	Humanoid/virus
		Reptilian
	Tracker
	Ben 10
Devaronian	Star Wars

Devilukean	To Love-Ru	Humanoid
	The Law-Twister Shorty and other stories by Gordon Dickson	Ursinoid
Dirdir	Jack Vance's Planet of Adventure Series
Dnyarri	Star Control
	Red Dwarf	Humanoid Canine
	Freelancer
Dominators	DC Comics	Humanoid
Dominators	Doctor Who	Ruthless humanoid conquerors; served by robotic Quarks.
DomZ	Beyond Good & Evil	Parasitic, energy-draining creatures with a skeletal/insectoid appearance. Come in various forms, including Sarcophagii, Spirit-Eaters and the DomZ High Priest.
Doog	Star Control 3	Reptiloid with canine features. Extremely dull-witted.
the Doublers	Stanisław Lem's Eden	two-in-one semi-humanoid
Douwd	Star Trek

	Barry B. Longyear's Enemy Mine and The Enemy Papers	Reptiloid
Draconians	Doctor Who	Reptilian humanoids with an interstellar empire rivalling that of Earth.
Draenei	World of Warcraft	Seven-foot-tall blue humanoids with cloven hooves for feet, reptilian tails, and barbels.
Drahvins	Doctor Who	Humanoid
Draic Kin	The Longest Journey, Dreamfall	Giant dragon-like creatures.
	Farscape	Insectile parasites
Drakh	Babylon 5 and Crusade	Reptiloids
Dralasite	Star Frontiers	Amoeba-like meter-tall spacefaring technological species
Drath	Galactic Civilizations: Altarian Prophecy	Pseudo-humanoid amoebae
Drayan	Star Trek	Humanoid
Dread Lords	Galactic Civilizations II: Dread Lords
Drej	Titan A.E.	Composed of pure energy, these aliens are a powerful force and are capable of destroying whole planets if they see fit. Ruled by a Queen.
Dremer	Gene Brewer's K-PAX
Drengin	Galactic Civilizations	Reptiloid
Drones (Yanme'e)	Halo	Flying creatures, appear insectoid. Part of Covenant Hierarchy, ill intent towards humans.
Drophyd	Ratchet & Clank	Intelligent fish-like creatures
Druuge	Star Control	Humanoid
Dugs	Star Wars	Reptiloids
Duos from Uranus	Space Patrol (1962)	Sapient semi-humanoid plants
Dubtaks	Ascendancy	large manta-like creature that move on a multitude of wormlike legs
Durlans	DC Comics' Legion of Super-Heroes	A mass of tentacles in robes.
	Star Wars	Reptiloid
Dyson Aliens	Peter F. Hamilton's "Pandora's Star"