| Seiko Obonai | |
| Nationality: | Japanese |
| Sport: | Athletics |
| Event: | Shot put |
| Birth Date: | 16 February 1940 |
| Birth Place: | Ninohe, Iwate, Japan |
| Death Place: | Tokyo, Japan |
[1] was a Japanese track and field athlete. She competed in the women's shot put at the 1964 Summer Olympics.[2]