Natsuo Kirino (桐野 夏生, Kirino Natsuo) is the pen name of Mariko Hashioka, a renowned Japanese novelist. Born on October 7, 1951, in Kanazawa, Ishikawa Prefecture, she is a leading figure in the recent boom of female writers of Japanese detective fiction.

Kirino was an active and spirited child, raised between her two brothers. Her father, an architect, moved the family to various cities, allowing her to spend her youth in Sendai and Sapporo before settling in Tokyo at fourteen, where she resides to this day. Kirino showed glimpses of her talent as a writer early on; she was a curious child who could immerse herself in her unique world of imagination.

After completing her law degree, Kirino worked in various fields before becoming a fiction writer. Her work has been recognized with awards such as the Naoki Prize.