- A-senee-ki-wakw
- A Caress of Twilight
- A Kiss of Shadows (novel)
- A Stroke of Midnight
- Aarakocra
- Aasimar
- Aatxe
- Abaddon
- Abarimon
- Abatwa
- Abchanchu
- Abcán
- Abdiel
- Aberewa
- Aberration (Dungeons & Dragons)
- Abhartach
- Abigor
- Abiku
- Abnuaaya
- Aboleth
- Abomination (Dungeons & Dragons)
- Abraxas
- Abumi-guchi
- Abura-akago
- Abura-sumashi
- Abyzou
- Accueil
- Achaierai
- Adamastor
- Adar Llwch Gwin
- Adaro
- Aditya
- Adlet
- Adlivun
- Adramelech
- Adrian Jeftichew
- Aegipane
- Aethon
- Af
- Afanc
- Afterlife
- Afturganga
- Agaliarept
- Agares
- Agchonion
- Agei
- Aghasura
- Agiel
- Agloolik
- Agnes of Glasgow
- Agogwe
- Ah Puch
- Ahiravan
- Ahlmakoh
- Ahmad Suradji
- Ahnfrau
- Ahool
- Ahriman
- Ahuizotl
- Aileen Wuornos
- Aim
- Airavata
- Airi
- Airitech
- Aitu
- Aitvaras
- Ajatar
- Akaname
- Akashita
- Akateko
- Akhkhazu
- Akhlut
- Akka
- Akkiyyini
- Akkorokamui
- Akupara
- Akurojin-no-hi
- Al
- Al Basti
- Al Rakim
- Ala
- Alanna Aquino
- Alastor
- Albastor
- Albawitch
- Albert Desalvo
- Albert Fish
- Alchemy
- Aleister Crowley
- Alerion
- Algernon Blackwood
- Alicanto
- Alice Elizabeth Doherty
- Alkonost
- Allocamelus
- Alloces
- Allu
- Almasty
- Alp-luachra
- Alpseid
- Alraun
- Altamaha-ha
- Alux
- Alû
- Amadan-na-Briona
- Amadan Dubh
- Amala
- Amalanhig
- Amalthea
- Amanojaku
- Amanozako
- Amarok
- Amarum
- Amaymyon
- Amazake-babaa
- Amdusias
- Amefurikozō
- Amemasu
- Ameonna
- Ameranthropoides loysi
- Amityville Horror
- Ammut
- Amomongo
- Amon
- Amphiptere
- Amphisbaena
- Amy
- Anahit
- Anansi
- Anatoly Onoprienko
- Anchimayen
- Andhaka
- Andras
- Andrealphus
- Andrei Chikatilo
- Andromalius
- Angel
- Angel (Dungeons & Dragons)
- Anggitay
- Anguirus
- Anguta
- Ani Hyuntikwalaski
- Animal elemental
- Anita Blake
- Ankou
- Anne Rice
- Annwn
- Antero Vipunen
- Anthropophagi
- AntiSocial Personality Disorder
- Anubis
- Ao Ao
- Aoandon
- Aoi Manto
- Aosagibi
- Apalala
- Apep
- Apis
- Apparitions
- Apsaras
- Arawn
- Aray
- Archdemon
- Archon
- Archon (Dungeons & Dragons)
- Archosaur
- Argippean
- Argopelter
- Argus
- Arimaspian
- Arkan Sonney
- Arthur Edward Waite
- Arulataq
- Aryaman
- Asag
- Asakku
- Asema
- Asena
- Ashi-magari
- Ashray
- Ashtar
- Ashva
- Asmodeus
- Aspidochelone
- Asrai
- Astaroth
- Astghik
- Astomi
- Asura
- Aswang
- Athach
- Atman
- Atshen
- Attorcroppe
- Atu
- Aufhocker
- Aughisky
- Auloniad
- Aumanil
- Auron
- Auseklis
- Auðumbla
- Aušrinė
- Avalerion
- Axehandle hound
- Axeman of New Orleans
- Ayakashi
- Ayida-Weddo
- Azazel
- Azeban
- Azhdahak
- Aziza
- Azrael
- Azukitogi
- Azure Dragon
- Ašvieniai
- BFRO
- Baal
- Baba Marta
- Baba Yaga
- Babi ngepet
- Backahasten
- Badaruc
- Bael
- Bahamut
- Bai Gu Jing
- Bai Ze
- Baihu
- Bajang
- Bakasura
- Bake-kujira
- Bakemono
- Bakeneko
- Bakezōri
- Bakki
- Bakru
- Baku
- Bakunawa
- Bal-Bal
- Balam
- Balaur
- Balayang
- Balderich
- Baldoon Mystery
- Balete Drive
- Ballybog
- Banasura
- Bandersnatch
- Bangpūtys
- Bannik
- Banshee
- Baobhan Sith
- Baphomet
- Baphomet (Dungeons & Dragons)
- Bar Juchne
- Baragon
- Barbatos
- Barbegazi
- Barghest
- Barghest (Dungeons & Dragons)
- Barmanou
- Barnacle goose
- Basajaun
- Basan
- Bashe
- Basilisco Chilote
- Basilisk
- Bast
- Bat
- Bathin
- Batibat
- Battra
- Bauchan
- Baugi
- Baykok
- Bear Lake Monster
- Beast of Bardia
- Beast of Billiwhack
- Beast of Bodmin
- Beast of Bray Road
- Beast of Busco
- Beast of Exmoor
- Beelzebub
- Befana
- Behemoth
- Beleth
- Belial
- Bell Witch
- Belphegor
- Bendith Y Mamau
- Bennu
- Berberoka
- Bergman's Bear
- Berith
- Berstuk
- Bessie
- Besta fera
- Betty Lou Williams
- Bhaga
- Bhairava
- Bhasmasura
- Bhuta
- Bible John
- Bicho-homem
- Bicorn
- Biddenden Maids (The)
- Biembien
- Bies
- Bifrons
- Big Muddy Monster
- Bigfoot
- Bigorne
- Bili Ape
- Billy Blind
- Bilocation
- Biollante
- Bisclavaret
- Bishop-fish
- Bizango
- Black Aggie
- Black Annis
- Black Dog
- Black Shuck
- Black Tortoise
- Black flash
- Black magic
- Blade
- Blanche Dumas
- Blankenfeldes manor
- Bleeding Tooth Fungus
- Blemmye
- Bloody Bones
- Bloody Mary
- Bluatschink
- Blue Lady
- Blue alien
- Blue tiger
- Blunderbore
- Bocánach
- Bodach
- Bogeyman
- Boggart
- Bogle
- Bokkenrijder
- Boky Hound