| Name | Meaning | Gender | Origin |
|---|
| Rex | King | Male | Latin |
| Riley | Rye clearing | Male | English |
| Rocket | To move swiftly and powerfully | Unisex | English |
| Rocky | Battle cry | Male | Germanic |
| Roger | Famous spear | Male | English |
| Rogue | | Unisex | Hebrew |
| Romeo | Pilgrim to Rome | Male | Italian |
| Roy | Red | Male | Gaelic |
| Rudy | Famous wolf | Male | Germanic |
| Rufus | Red | Male | Latin |
| Rusty | Rusty, full of rust | Unisex | American English |
| Ryan | Little King | Male | Gaelic |
| 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 |
| Sarge | Noncommissioned Army or Air Force rank | Unisex | English |
| Sasha | Defending men | Unisex | Greek |
| Sassy | Lively and spirited | Unisex | English |
| Scooter | One who goes suddenly and speedily. | Unisex | English |
| Scout | Observer | Unisex | American English |
| Shadow | Shadow | Unisex | English |
| Shaggy | Bushy and matted (hair), unkempt. | Unisex | English |
| Shea | Hawklike - graceful, free, courageous | Male | Gaelic |
| Sherlock | With cropped hair | Male | English |
| Shorty | Of less than average size | Unisex | English |
| Silly | | Unisex | Hebrew |
| Skipper | Master of a Ship | Male | American English |
| Smoky | | Unisex | Hebrew |