| Shinya Adachi | |
| Native Name: | 足立 信也 |
| Birth Name: | Adachi Shin'ya |
| Birth Date: | 5 June 1957 |
| Party: | Independent |
| Otherparty: | DPJ DP DPP |
| Term Start: | 24 April 2023 |
| Constituency1: | Ōita at-large district |
| Term Start1: | 26 July 2004 |
| Term End1: | 25 July 2022 |
| Birth Place: | Ōita, Ōita, Japan |
| Alma Mater: | University of Tsukuba |
| Website: | 足立信也ホームページ |
is a Japanese politician of the Democratic Party for the People, and a former member of the House of Councillors in the Diet (national legislature).
A native of Ōita, Ōita, he attended University of Tsukuba and received a Ph.D. in medicine from it. He was elected for the first time in 2004. He served until 2022, and in 2023 he became the mayor of Ōita city.[1]