| Koichi Takemasa | |
| Native Name Lang: | ja |
| Office: | Member of the House of Representatives |
| Constituency: | Northern Kanto PR |
| Term Start: | 1 November 2024 |
| Constituency1: | Saitama 1st |
| Term Start1: | 26 June 2000 |
| Term End1: | 28 September 2017 |
| Predecessor1: | Hikaru Matsunaga |
| Successor1: | Hideki Murai |
| Office2: | Member of the Saitama Prefectural Assembly |
| Constituency2: | South 3rd |
| Term Start2: | 1995 |
| Term End2: | 2000 |
| Birth Date: | 23 March 1961 |
| Birth Place: | Shimizu, Shizuoka, Japan |
| Party: | CDP |
| Otherparty: | DPJ DP Kibō no Tō |
| Alma Mater: | Keio University |
is a Japanese politician serving in the House of Representatives in the Diet (national legislature) as a member of the Constitutional Democratic Party. A native of Shimizu, Shizuoka and graduate of Keio University he was elected for the first time in 1995 after an unsuccessful run in 1991.