| Name | Meaning | Gender | Origin |
|---|
| Rufus | Red | Male | Latin |
| Rusty | Rusty, full of rust | Unisex | American English |
| Ryder | One who rides | Unisex | English |
| Sable | Sable (black) | Unisex | English |
| Sabre | | Unisex | Hebrew |
| Sam | He is called god | Male | Hebrew |
| Sammy | His name is God | Unisex | Hebrew |
| Samson | Sun | Male | Hebrew |
| Sandy | Defending men | Male | Greek |
| Sasha | Defending men | Unisex | Greek |
| Sassy | Lively and spirited | Unisex | English |
| Satan | The Devil and adversary of God | Unisex | English |
| Scout | Observer | Unisex | American English |
| Sebastian | Man from Sebaste | Male | Latin |
| Shadow | Shadow | Unisex | English |
| Shilo | Gift for him | Unisex | Hebrew |
| Sky | Sky | Unisex | Norse |
| Smokey | A grayish blue colour. Slang for highway patrol officer | Unisex | English |
| Smokie | | Unisex | Hebrew |
| Smoky | | Unisex | Hebrew |
| Smudge | A blotch or smear | Unisex | English |
| Snoopy | | Unisex | Hebrew |
| Socks | Short stockings finishing above the ankle | Unisex | English |
| Sooty | Covered with soot | Unisex | English |
| Sparky | Animated, lively. | Unisex | English |
| Spike | A long, thick sharp-pointed piece of wood or metal | Male | English |
| Spirit | Part of the human being associated with the mind. Vigorous or animated state - spirited. Also distilled alcohol. | Unisex | English |
| Spot | After Data's cat on Star Trek: The Next Generation | Unisex | English |
| Spud | Slang for potato. | Unisex | English |
| Stormy | Violent weather | Unisex | English |