List of fictional alien species: B
| Name | Source | Type |
|---|---|---|
| Baalols | Perry Rhodan | |
| Babel fish | The Hitchhiker's Guide to the Galaxy | A universal translator; a small yellow leech-like fish that telepathically translates all languages into one the wearer knows after inserting it in his ear. |
| Badoon | Marvel Comics | |
| Bahmi | Rift: Planes of Telara | Descendants of humans and air spirits. Large blue- or violet-skinned humanoids. |
| Bailies | Cleopatra 2525 | Machine race that conquered Earth |
| Bajoran | Star Trek | Humanoid |
| Ba'ku | Star Trek | |
| Baliflids | Ascendancy | |
| Ballchinnian | Men in Black II | |
| Balmarian | Super Robot Wars | |
| Baltan | Ultraman | Space ninja |
| Bane | The Sarah Jane Adventures | Large tentacled aliens |
| Bandersnatchi | Larry Niven's Known Space | Artificially engineered single-celled gastropod, twice the size of a brontosaurus. Slaver's meat animal, sentient. Agree to be hunted for sport in exchange for currency to purchase mechanical arms. Asexual reproduction, impervious to genetic degradation or mutation. |
| Bandi | Star Trek | Humanoid |
| Banik | Farscape | Humanoid |
| Bannermen | Doctor Who | Humanoid |
| Bantha | Star Wars | Huge hairy beasts of burden |
| Barkonides | Perry Rhodan | |
| Barzans | Star Trek | |
| Battle Cupcakes | Bravest Warriors | The Battle Cupcakes were engineered by Danny to fight to the complete and utter death. |
| Baufrin | Renegade Legion | Insectoid centauroid |
| Beings of the Extra Terrestrial origin which is Adversary of human race | Muv-Luv | |
| Benjari | Battlelords of the 23rd Century | |
| Benzite | Star Trek | |
| Berellian | Star Trek | |
| Berserkers | Fred Saberhagen's Berserker series | |
| Berubelan | Anachronox | |
| Besalisk | Star Wars | Four arms |
| Betazoid | Star Trek | Empathic humanoids |
| Bgztl | DC Comics Legion of Super-Heroes | |
| Bioroids | Intense Stories | |
| Bith | Star Wars | |
| Bismollian | DC Comics' Legion of Super-Heroes | |
| Bjorn | Space Quest | |
| Black Arms | Shadow the Hedgehog | Humanoid |
| Black Cloud | Fred Hoyle | Interstellar dust cloud |
| Black Oil | The X-Files | |
| Blastaar | Marvel Comics | Native of the Negative Zone |
| Blathereen | Doctor Who | Raxacoricofallapatorian |
| Blisk | Destroy All Humans! 2 | Bipedal, armoured crustaceans with a hive mind and a dependence on radiation. Former natives of Mars. |
| Blobs | Invader Zim | |
| Bolian | Star Trek | Blue-skinned humanoids |
| Boolite | Farscape | Humanoid |
| Borg | Star Trek | A race of cybernetically enhanced life forms from the Delta Quadrant of the Milky Way Galaxy. Able to assimilate almost any life form into their collective hive-mind and able to adapt to all forms of offensive capability instantly. |
| Bothans | Star Wars | Humanoid |
| Braalians | DC Comics' Legion of Super-Heroes | |
| Bradicor | Schlock Mercenary | |
| Brain Dogs | Bravest Warriors | |
| Brainiac | Smallville | |
| Brains | The Adventures of Jimmy Neutron: Boy Genius ("Win, Lose and Kaboom") | |
| Brakiri | Babylon 5 | Primarily night dwellers |
| Breen | Star Trek | Humanoid |
| Brelac | McKenzie Files | A reptilian alien race originating from Old Earth. |
| Bricker | Star Trek | |
| Briori | Star Trek | |
| Brood | Marvel Comics | |
| Brunnen G | LEXX | Humanoid |
| Brunali | Star Trek | |
| Brutes (Jiralhanae) | Halo | Pack mentality humanoids of great physical standing. Part of a larger group known as the "Covenant". Intensely loyal to their religious beliefs, intent on completely wiping out the human race. |
| Budong | Farscape | |
| Bugs from Klendathu | Starship Troopers | |
| Bulrathi | Master of Orion | |
| Buggers | Ender's Game series | A hive mind species resembling insects. Invaded Earth twice before being destroyed at their home world by Andrew 'Ender' Wiggin. |
| Bunless People | Bravest Warriors | The Bunless people inhabit the planet Bunless 9 and have no buns. |
| Bynar | Star Trek |