| Spirit naga | 8 | Monstrosity | Large | 15 | 75 | | chaotic evil | | Monster Manual (SRD) | 18 | 17 | 14 | 16 | 15 | 16 |
| Spirit troll | 11 | Giant | Large | 17 | 97 | | chaotic evil | | Mordenkainen's Tome of Foes | | | | | | |
| Spring eladrin | 10 | Fey (elf) | Medium | 19 | 127 | | chaotic neutral | | Mordenkainen's Tome of Foes | | | | | | |
| Sprite | 0.25 | Fey | Tiny | 15 | 2 | fly | neutral good | | Monster Manual (SRD) | 3 | 18 | 10 | 14 | 13 | 11 |
| Spy | 1 | Humanoid (any race) | Medium | 12 | 27 | | any alignment | | Monster Manual (SRD) | 10 | 15 | 10 | 12 | 14 | 16 |
| Star spawn grue | 0.25 | Aberration | Small | 11 | 17 | | neutral evil | | Mordenkainen's Tome of Foes | | | | | | |
| Star spawn hulk | 10 | Aberration | Large | 16 | 136 | | chaotic evil | | Mordenkainen's Tome of Foes | | | | | | |
| Star spawn larva mage | 16 | Aberration | Medium | 16 | 168 | | chaotic evil | | Mordenkainen's Tome of Foes | | | | | | |
| Star spawn mangler | 5 | Aberration | Medium | 14 | 71 | | chaotic evil | | Mordenkainen's Tome of Foes | | | | | | |
| Star spawn seer | 13 | Aberration | Medium | 17 | 153 | | neutral evil | | Mordenkainen's Tome of Foes | | | | | | |
| Steam mephit | 0.25 | Elemental | Small | 10 | 21 | fly | neutral evil | | Monster Manual (SRD) | 5 | 11 | 10 | 11 | 10 | 12 |
| Steel predator | 16 | Construct | Large | 20 | 207 | | lawful evil | | Mordenkainen's Tome of Foes | | | | | | |
| Stegosaurus | 4 | Beast | Huge | 13 | 76 | | unaligned | | Adventures (Tomb of Annihilation) | | | | | | |
| Stirge | 0.12 | Beast | Tiny | 14 | 2 | fly | unaligned | | Monster Manual (SRD) | 4 | 16 | 11 | 2 | 8 | 6 |
| Stone cursed | 1 | Construct | Medium | 17 | 19 | | lawful evil | | Mordenkainen's Tome of Foes | | | | | | |
| Stone giant | 7 | Giant | Huge | 17 | 126 | | neutral | | Monster Manual (SRD) | 23 | 15 | 20 | 10 | 12 | 9 |
| Stone giant dreamwalker | 10 | Giant (stone giant) | Huge | 18 | 161 | | chaotic neutral | | Volo's Guide to Monsters | 23 | 14 | 21 | 10 | 8 | 12 |
| Stone golem | 10 | Construct | Large | 17 | 178 | | unaligned | | Monster Manual (SRD) | 22 | 9 | 20 | 3 | 11 | 1 |
| Stone juggernaut | 12 | Construct | Large | 15 | 157 | | unaligned | | Adventures (Tomb of Annihilation) | | | | | | |
| Storm giant | 13 | Giant | Huge | 16 | 230 | swim | chaotic good | | Monster Manual (SRD) | 29 | 14 | 20 | 16 | 18 | 18 |
| Storm giant quintessent | 16 | Giant (storm giant) | Huge | 12 | 230 | fly, swim | chaotic good | | Volo's Guide to Monsters | | | | | | |
| Su monster | 1 | Monstrosity | Medium | 12 | 27 | | chaotic evil | | Adventures (Tomb of Annihilation) | | | | | | |
| Succubus | 4 | Fiend (shapechanger) | Medium | 15 | 66 | fly | neutral evil | | Monster Manual (SRD) | 8 | 17 | 13 | 15 | 12 | 20 |
| Summer eladrin | 10 | Fey (elf) | Medium | 19 | 127 | | chaotic neutral | | Mordenkainen's Tome of Foes | | | | | | |
| Swarm of bats | 0.25 | Swarm of Tiny beasts | Medium | 12 | 22 | fly | unaligned | | Monster Manual (SRD) | 5 | 15 | 10 | 2 | 12 | 4 |