| Tatsuomi Koishi 小石 龍臣 | |
| Fullname: | Tatsuomi Koishi |
| Birth Date: | 22 August 1977 |
| Birth Place: | Tosu, Saga, Japan |
| Position: | Midfielder, Forward |
| Youthyears1: | 1993–1995 |
| Youthclubs1: | Higashi Fukuoka High School |
| Youthyears2: | 1996–1999 |
| Youthclubs2: | Rissho University |
| Years1: | 2000–2005 |
| Clubs1: | Sagan Tosu |
| Caps1: | 141 |
| Goals1: | 15 |
| Years2: | 2006 |
| Clubs2: | ALO's Hokuriku |
| Caps2: | 16 |
| Goals2: | 3 |
| Totalcaps: | 157 |
| Totalgoals: | 18 |
is a former Japanese football player.
Koishi was born in Tosu on August 22, 1977. After graduating from Rissho University, he joined the J2 League club Sagan Tosu based in his local area in 2000. He played often as a forward during his first season. In 2003, he played as an offensive midfielder. However he was not played in 2005. In 2006, he moved to the Japan Football League club ALO's Hokuriku. He retired at the end of the 2006 season.
| Club performance | League | Cup | League Cup | Total | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Season | Club | League | Apps | Goals | Apps | Goals | Apps | Goals | Apps | Goals | |
| Japan | League | Emperor's Cup | J.League Cup | Total | |||||||
| 2000 | Sagan Tosu | J2 League | 22 | 4 | 2 | 0 | 2 | 0 | 26 | 4 | |
| 2001 | 19 | 6 | 0 | 0 | 0 | 0 | 19 | 6 | |||
| 2002 | 31 | 3 | 1 | 0 | colspan="2" | - | 32 | 3 | |||
| 2003 | 29 | 0 | 1 | 0 | colspan="2" | - | 30 | 0 | |||
| 2004 | 39 | 2 | 1 | 0 | colspan="2" | - | 40 | 2 | |||
| 2005 | 1 | 0 | 0 | 0 | colspan="2" | - | 1 | 0 | |||
| 2006 | ALO's Hokuriku | Football League | 16 | 3 | colspan="2" | - | colspan="2" | - | 16 | 3 | |
| Career total | 157 | 18 | 5 | 0 | 2 | 0 | 164 | 18 | |||