| Masahiro Koga 古賀 正紘 | |
| Fullname: | Masahiro Koga |
| Birth Date: | 8 September 1978 |
| Birth Place: | Okawa, Fukuoka, Japan |
| Position: | Defender |
| Youthyears1: | 1994–1996 |
| Youthclubs1: | Higashi Fukuoka High School |
| Years1: | 1997–2006 |
| Clubs1: | Nagoya Grampus Eight |
| Caps1: | 231 |
| Goals1: | 15 |
| Years2: | 2007–2010 |
| Clubs2: | Kashiwa Reysol |
| Caps2: | 78 |
| Goals2: | 5 |
| Years3: | 2010–2011 |
| Clubs3: | Júbilo Iwata |
| Caps3: | 19 |
| Goals3: | 0 |
| Years4: | 2012–2015 |
| Clubs4: | Avispa Fukuoka |
| Caps4: | 74 |
| Goals4: | 1 |
| Totalcaps: | 402 |
| Totalgoals: | 21 |
| Nationalyears1: | 1995 |
| Nationalteam1: | Japan U-17 |
| Nationalcaps1: | 3 |
| Nationalgoals1: | 0 |
is a former Japanese football player. His younger brother Seiji is also a footballer.
Koga was born in Okawa on September 8, 1978. After graduating from high school, he joined the Nagoya Grampus Eight in 1997. He became a regular player as a center back from 1998. The club won the 1999 Emperor's Cup. He moved to Kashiwa Reysol in 2007. Although he played as a regular player, he lost his place due to an injury in 2010. He then moved to Júbilo Iwata in August 2010. After playing for two seasons, he moved to his local club Avispa Fukuoka in 2012. He retired at the end of the 2015 season.
In August 1995, Koga was selected by the Japan U-17 national team for the 1995 U-17 World Championship and he played full time in all three matches. In June 1997, he was also selected by the Japan U-20 national team for the 1997 World Youth Championship, but he did not play in any matches.
| 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 | |||||||
| 1997 | Nagoya Grampus Eight | J1 League | 8 | 0 | 1 | 0 | 5 | 0 | 14 | 0 | |
| 1998 | 21 | 0 | 0 | 0 | 0 | 0 | 21 | 0 | |||
| 1999 | 26 | 2 | 5 | 0 | 4 | 0 | 35 | 2 | |||
| 2000 | 25 | 2 | 1 | 0 | 4 | 0 | 30 | 2 | |||
| 2001 | 18 | 0 | 0 | 0 | 3 | 0 | 21 | 0 | |||
| 2002 | 28 | 1 | 3 | 0 | 6 | 0 | 37 | 1 | |||
| 2003 | 28 | 2 | 2 | 0 | 4 | 0 | 34 | 2 | |||
| 2004 | 24 | 1 | 2 | 1 | 7 | 0 | 33 | 2 | |||
| 2005 | 27 | 5 | 1 | 0 | 6 | 0 | 34 | 5 | |||
| 2006 | 26 | 2 | 0 | 0 | 5 | 0 | 31 | 2 | |||
| 2007 | Kashiwa Reysol | J1 League | 29 | 2 | 1 | 0 | 2 | 1 | 32 | 3 | |
| 2008 | 29 | 1 | 5 | 1 | 5 | 1 | 39 | 3 | |||
| 2009 | 20 | 2 | 0 | 0 | 4 | 0 | 24 | 2 | |||
| 2010 | J2 League | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||
| 2010 | Júbilo Iwata | J1 League | 12 | 0 | 2 | 0 | 3 | 0 | 17 | 0 | |
| 2011 | 7 | 0 | 1 | 0 | 2 | 0 | 10 | 0 | |||
| 2012 | Avispa Fukuoka | J2 League | 33 | 1 | 2 | 0 | - | - | 35 | 1 | |
| 2013 | 22 | 0 | 0 | 0 | 0 | 0 | 22 | 0 | |||
| 2014 | 13 | 0 | 1 | 0 | 0 | 0 | 14 | 0 | |||
| 2015 | 6 | 0 | 0 | 0 | 0 | 0 | 6 | 0 | |||
| Total | 402 | 21 | 27 | 2 | 60 | 2 | 489 | 25 | |||