| O | |
| Type: | Album |
| Artist: | Eiko Shimamiya |
| Cover: | O Eiko Shimamiya.jpg |
| Released: | 4 October 2006 |
| Recorded: | 2005–2006 |
| Genre: | J-pop |
| Length: | 1 hour 1 min 58 sec |
| Label: | Geneon |
| Producer: | I've |
| Prev Title: | Endless Loop |
| Prev Year: | 2005 |
| Next Title: | Hikari Nadeshiko |
| Next Year: | 2008 |
O is the first full-length album from Eiko Shimamiya, it includes the hit single Higurashi no Naku Koro ni (opening from the same-titled anime). A limited edition with a DVD including the music video of Higurashi no Naku Koro ni is available. The album charted for five weeks on the Oricon charts and sold 10,000 copies.