| Sign | |
| Cover: | FLOWSignReg.jpg |
| Type: | single |
| Artist: | FLOW |
| Released: | January 13, 2010 |
| Label: | Ki/oon Records |
| Prev Title: | Snow Flake ~Kioku no Koshitsu~ / Pulse |
| Prev Year: | 2008 |
| Next Title: | CALLING |
| Next Year: | 2010 |
Sign is FLOW's eighteenth single. Its A-Side was used as the sixth opening theme song for Naruto Shippuden. The single has two editions: regular and limited. The limited edition includes a bonus CD with extra tracks, a wide cap sticker, double-sided jacket, and Sharingan sticker. It reached number 4 on the Oricon charts in its first week and charted for 6 weeks.[1]