| The Water Spirit of Oath | |
|---|---|
 Cover | |
| Author(s) | Yamaguchi Noboru |
| Original title | 誓約の水精霊 |
| Illustrator | Usatsuka Eiji |
| Country | Japan |
| Language | Japanese |
| Series | The Familiar of Zero |
| Genre(s) | Fantasy |
| Publisher | MF Bunko J |
| Media type | |
| Preceded by | The Founder's Prayer Book |
| Followed by | A Holiday in Tristania |
The Water Spirit of Oath is the fourth volume of the light novel series The Familiar of Zero.