Hisaya Naoki, born Hayashi Naoki (林直樹, is a Japanese screenwriter who has worked for Tactics, Key and Siesta, but as of 2006, he is a freelance writer. He is well known for being the main writer of the popular visual novel Kanon while working under Key. Additional works include Moon., One: Kagayaku Kisetsu e, and Moon Childe. He is also known for being the original concept writer for Sola. He also does work in a doujin circle named Cork Board.

Hisaya Naoki debuted as the main scenario writer for the adult visual novel developer Tactics under Nexton in 1997. He first worked on the company's second title Moon., followed by One: Kagayaku Kisetsu e in 1998. After One's completion, Hisaya and much of the staff who made both Moon. and One, including Maeda Jun, Itaru Hinoue, Shinji Orito, and OdiakeS, left Tactics to work under the video game publishing company Visual Art's where they formed the company Key. At Key, Hisaya worked on the planning and most of the scenario for Kanon, released in 1999, but following the completion of Kanon, quit Key. Afterwards, Hisaya formed a doujin circle and participated at Comiket and C Revo, another comic convention, between 1999 and 2002.

In 2003, Hisaya became involved with the doujin circle "Black box" where he was put in charge of their first doujin visual novel Limit Off. Hisaya was even able to write the lyrics for the game's theme song "Real intention," something he had never done before. However, even with anticipation mounting, in August 2003, the project was frozen and has never been restarted again. In 2004, Hisaya started working for the video game company Siesta where he contributed as a sub-writer for their first title Moon Childe released in December 2005.

Afterwards, Hisaya once again quit the company he was working for, but at Comiket 70 in August 2006, it was announced that he would now be working with illustrator Nanao Naru on a series entitled Sola as the main concept writer. When Sola was adapted into an anime in 2007, Hisaya was in charge of five out of fifteen episodes of the screenplay. He is also the author of the Sola manga series, illustrated by Chako Abeno.