Hotarubi no Mori e (Japanese: 蛍火の杜へ, lit. 'Into the Forest of Fireflies' Light') is a one-shot shōjo manga written by Yuki Midorikawa. It was published in the July 2002 issue of LaLa DX in Japan, and in July 2003 it was reprinted in a tankōbon short story collection of the same name, which included four romantic one-shot stories written by Midorikawa. Hotarubi no Mori e tells the story of a young girl named Hotaru and her friendship with Gin, a strange young man wearing a mask, who she meets at the age of six in a mountain forest near her grandfather's country home. Hotaru learns that her friend is supernatural and that touching Gin will cause him to disappear forever. Hotaru returns every summer to spend time with Gin, and their relationship matures as both struggle with its limitations. The inspiration to write the story came suddenly to Midorikawa, who immediately drew the manga—a process that went smoothly despite some initial conflicting elements. Hotarubi no Mori e is considered a starting point for Midorikawa's best-known work, Natsume's Book of Friends.

A 44-minute anime film with the same title was produced in 2011 at the anime studio Brain's Base and directed by Takahiro Omori. The film starred Japanese voice actors Ayane Sakura and Kōki Uchiyama, and its soundtrack included music by Makoto Yoshimori. The film maintained a strong following for months in Japan after its opening on September 17, 2011. The European premiere of Hotarubi no Mori e was on October 8, 2011, at the Scotland Loves Animation festival, where it won the Jury Prize. It was screened at the Leeds International Film Festival, Anime Contents Expo and Anime Expo convention, and also won the Animation Film Award at the 66th Annual Mainichi Film Awards.

The anime was released on Blu-ray Disc (BD) and DVD in Japan on February 22, 2012. An additional story related to the original manga and anime film, titled Hotarubi no Mori e Tokubetsuhen (蛍火の杜へ 特別編), was released in a keepsake edition of the manga 12 days prior to the release of the anime. Both the keepsake edition manga and the limited edition BD ranked No. 13 on Japan's Oricon sales chart shortly after their release. Sakura reported experiencing a strong emotional reaction to the story while recording the voice of Hotaru, and Midorikawa acknowledged that the story had a positive impact on her career. Reviewers universally praised the anime film for its beauty, simplicity, and tenderness, likening it to the works of Hayao Miyazaki of Studio Ghibli and Makoto Shinkai. There were few criticisms, most commonly focusing on its short length.