Creature Codex (web)     Pathfinder original/official source
The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Pathfinder 1e Bestiary 1     Pathfinder original/official source
Pathfinder 1e Bestiary 3     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Pathfinder 2e Bestiary 3     Pathfinder original/official source
Book Of The Damned     Pathfinder original/official source
Mythic Adventures     Pathfinder original/official source
Monster Classes: Sand And Spirit     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
Monster Manual Expanded v1     D&D 5e original/official source
Old Gus: Plantfolk, Undead, And Other Oddities     D&D 5e original/official source
Asian Monsters     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual     D&D 4e (no source link)
Dungeons And Dragons Essentials: Monster Vault     D&D 4e (no source link)
Monster Manual 3     D&D 3e original/official source
Dragon Magazine Monster Ecologies     D&D 2e/3e (no source link)
MojoBob (web)     D&D 2e original/official source
D&D 2e Monstrous Manual     D&D 2e original/official source
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
AD&D Monster Manual     AD&D 1e (no source link)
13th Age Bestiary 2     13th Age (no source link)
Hacklopedia Of Beasts     Hackmaster original/official source
Blackdirge's Dungeon Denizens     Dungeon Crawl Classics (no source link)
Baby Bestiary 1     Any original/official source