| Name | Meaning | Gender | Origin |
|---|
| Rosco | Roe deer wood | Unisex | Norse |
| Roscoe | Roe deer wood | Male | Norse |
| Rowdy | Boisterous. Western Nickname. | Unisex | English |
| Roxie | Star | Unisex | Persian |
| Rufus | Red | Male | Latin |
| Rusty | Rusty, full of rust | Unisex | American 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 |
| Sasquatch | Has extra toes and hence is a bigfoot | Unisex | English |
| Sassy | Lively and spirited | Unisex | English |
| Satan | The Devil and adversary of God | Unisex | English |
| Saturn | Sixth and second largest planet away from the Sun. | Unisex | English |
| Scooter | One who goes suddenly and speedily. | Unisex | English |
| Scout | Observer | Unisex | American English |
| Shark | | Unisex | Hebrew |
| Shiloh | Gift for him | Unisex | Hebrew |
| Shorty | Of less than average size | Unisex | English |
| Silver | Silver (the metal or colour) | Male | English |
| Skinny | | Unisex | Hebrew |
| Skip | Master of a Ship | Male | American English |
| Skipper | Master of a Ship | Male | American English |
| Sky | Sky | Unisex | Norse |
| Smiley | | Unisex | Hebrew |
| Smokey | A grayish blue colour. Slang for highway patrol officer | Unisex | English |
| Snake | | Unisex | Hebrew |
| Solo | | Unisex | Hebrew |