| 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. |
| Dakkamites | 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. |
| The Dance | 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 | |
| Darrians | Traveller | |
| Darzok | Haegemonia: Legions of Iron | |
| Daxamites | DC Comics | A humanoid species who are related to Kryptonians and possess similar abilities to them, but are vulnerable to lead rather than Kryptonite. |
| Death Angels | A Quiet Place | Blind apex predators that hunt by sound. |
| Decapodian | Futurama | A humanoid crustacean-like species originating from the planet Decapod 10. Zoidberg, a main character in the series and a member of the Planet Express crew, is a Decapodian. |
| 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 | A band of many different races |
| Delphons | 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 | |
| Deneans | Fstar trek | Humanoid |
| Denebians | Star Wars | |
| Deng | Keith Laumer's Bolo series | Arachnoids |
| Denobulans | Star Trek | Humanoid |
| Dentics | 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". |
| Derkuhr | Chronicles of Honor | Reptilian |
| Dessarians | Tracker | |
| Detrovite | Ben 10 | A humanoid species originating from an unknown planet with an extremely high average temperature. Vulkanus, a recurring enemy of Ben Tennyson, is a Detrovite. |
| Devaronian | Star Wars | |
| Devastators | One Mind's Eye | |
| Devilukean | To Love-Ru | Humanoid |
| Dilbians | The Law-Twister Shorty and other stories by Gordon Dickson | Ursinoid |
| Dirdir | Jack Vance's Planet of Adventure Series | |
| Dnyarri | Star Control | |
| Do Min-joon | My Love from the Star | Humanoid |
| Do Seo-joon | Oppa, Saranghae! | A humanoid character pulled out this TV show |
| Dog | Red Dwarf | Humanoid Canine |
| Dom Kavash | Freelancer | |
| Dominators | DC Comics | A humanoid species who reside in an advanced, hierarchical society. The Dominators are skilled geneticists and can manipulate the metagene to enhance themselves and others. |
| 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. |
| Doraemon | Doraemon | Robot who is gender-swapped version of Doraemon |
| the Doublers | Stanisław Lem's Eden | two-in-one semi-humanoid |
| Douwd | Star Trek | |
| Draags | Stefan Wul's Oms en série | Giant humanoids |
| Draaknaars | Thor series | |
| Dracs | 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. |
| Drak | 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. |
| Drell | Mass Effect | Reptiloids. Rescued by and serve the Hanar species. |
| Dremer | Gene Brewer's K-PAX | |
| Drengin | Galactic Civilizations | Reptiloid |
| Drones | Halo | Flying creatures, appear insectoid. Part of Covenant Hierarchy, ill intent towards humans. |
| Drophyd | Ratchet & Clank | Intelligent fish-like creatures |
| Druuge | Star Control | Humanoid |
| Dubtaks | Ascendancy | A large manta-like creature with many legs. |
| Dugs | Star Wars | Reptiloids |
| Duos from Uranus | Space Patrol (1962) | Sapient semi-humanoid plants |
| Duo Miaomiao | Let's Shake It | Humanoid |
| Duo Xingxing | Let's Shake It | Humanoid |
| Durlan | DC Comics | A species from the planet Durla who possess shapeshifting abilities. Left unable to remember their original form after being affected by radiation, the Durlans took on a form resembling a mass of tentacles. However, they generally assume a humanoid form when outside Durla. |
| Duros | Star Wars | Reptiloid |
| Dyson Aliens | Peter F. Hamilton's "Pandora's Star" | |