| Ambush drake | 0.5 | Dragon | Medium | 13 | 22 | | unaligned | | Adventures (Tyranny of Dragons) | | | | | | |
| Amnizu | 18 | Fiend (devil) | Medium | 21 | 202 | fly | lawful evil | | Mordenkainen's Tome of Foes | | | | | | |
| Ancient black dragon | 21 | Dragon | Gargantuan | 22 | 367 | fly, swim | chaotic evil | Legendary | Monster Manual (SRD) | 27 | 14 | 25 | 16 | 15 | 19 |
| Ancient blue dragon | 23 | Dragon | Gargantuan | 22 | 481 | fly | lawful evil | Legendary | Monster Manual (SRD) | 29 | 10 | 27 | 18 | 17 | 21 |
| Ancient brass dragon | 20 | Dragon | Gargantuan | 20 | 297 | fly | chaotic good | Legendary | Monster Manual (SRD) | 27 | 10 | 25 | 16 | 15 | 19 |
| Ancient bronze dragon | 22 | Dragon | Gargantuan | 22 | 444 | fly, swim | lawful good | Legendary | Monster Manual (SRD) | 29 | 10 | 27 | 18 | 17 | 21 |
| Ancient copper dragon | 21 | Dragon | Gargantuan | 21 | 350 | fly | chaotic good | Legendary | Monster Manual (SRD) | 27 | 12 | 25 | 20 | 17 | 19 |
| Ancient gold dragon | 24 | Dragon | Gargantuan | 22 | 546 | fly, swim | lawful good | Legendary | Monster Manual (SRD) | 30 | 14 | 29 | 18 | 17 | 28 |
| Ancient green dragon | 22 | Dragon | Gargantuan | 21 | 385 | fly, swim | lawful evil | Legendary | Monster Manual (SRD) | 27 | 12 | 25 | 20 | 17 | 19 |
| Ancient red dragon | 24 | Dragon | Gargantuan | 22 | 546 | fly | chaotic evil | Legendary | Monster Manual (SRD) | 30 | 10 | 29 | 18 | 15 | 23 |
| Ancient shadow | 1 | Undead | Medium | 13 | 32 | | chaotic evil | | Extra (AideDD) | 6 | 16 | 14 | 6 | 10 | 8 |
| Ancient silver dragon | 23 | Dragon | Gargantuan | 22 | 487 | fly | lawful good | Legendary | Monster Manual (SRD) | 30 | 10 | 29 | 18 | 15 | 23 |
| Ancient white dragon | 20 | Dragon | Gargantuan | 20 | 333 | fly, swim | chaotic evil | Legendary | Monster Manual (SRD) | 26 | 10 | 26 | 10 | 13 | 14 |
| Androsphinx | 17 | Monstrosity | Large | 17 | 199 | fly | lawful neutral | Legendary | Monster Manual (SRD) | 22 | 10 | 20 | 16 | 18 | 23 |
| Animated armor | 1 | Construct | Medium | 18 | 33 | | unaligned | | Monster Manual (SRD) | 14 | 11 | 13 | 1 | 3 | 1 |
| Ankheg | 2 | Monstrosity | Large | 14 | 39 | | unaligned | | Monster Manual (SRD) | 17 | 11 | 13 | 1 | 13 | 6 |
| Ankylosaurus | 3 | Beast | Huge | 15 | 68 | | unaligned | | Monster Manual (SRD) | 19 | 11 | 15 | 2 | 12 | 5 |
| Annis hag | 6 | Fey | Large | 17 | 75 | | chaotic evil | | Volo's Guide to Monsters | 21 | 12 | 14 | 13 | 14 | 15 |
| Ape | 0.5 | Beast | Medium | 12 | 19 | | unaligned | | Monster Manual (SRD) | 16 | 14 | 14 | 6 | 12 | 7 |
| Apprentice wizard | 0.25 | Humanoid (any race) | Medium | 10 | 9 | | any alignment | | Volo's Guide to Monsters | | | | | | |
| Arcanaloth | 12 | Fiend (yugoloth) | Medium | 17 | 104 | fly | neutral evil | | Monster Manual | | | | | | |
| Archdruid | 12 | Humanoid (any race) | Medium | 16 | 132 | | any alignment | | Volo's Guide to Monsters | | | | | | |
| Archer | 3 | Humanoid (any race) | Medium | 16 | 75 | | any alignment | | Volo's Guide to Monsters | | | | | | |
| Archmage | 12 | Humanoid (any race) | Medium | 12 | 99 | | any alignment | | Monster Manual (SRD) | 10 | 14 | 12 | 20 | 15 | 16 |
| Armanite | 7 | Fiend (demon) | Large | 16 | 84 | | chaotic evil | | Mordenkainen's Tome of Foes | | | | | | |