Nobuko Yoshiya (吉屋 信子, Yoshiya Nobuko; 12 January 1896 – 11 July 1973) was a Japanese novelist active in Taishō and Shōwa period Japan. She was one of modern Japan's most commercially successful and prolific writers, specializing in serialized romance novels and adolescent girls' fiction, as well as being a pioneer in Japanese lesbian literature, including the Class S genre. Several of her stories have been made into films.

Yoshiya was born in Niigata Prefecture, but grew up in Mooka and Tochigi cities in Tochigi Prefecture. Her father was first a police officer and then became a local county government official, so her family relocated often to accommodate his transfers. She was the only daughter and youngest of five children in her family. Both her mother and her father came from samurai families. Her middle-class, culturally conservative parents trained her for the "good wife, wise mother" role expected of women in Meiji Japan. Her literary career began when she was in her teens.

In 1915, she moved to Tokyo, where she began to diverge from Japan's gender expectations. Yoshiya often dressed in an androgynous style, including in magazine photo sessions. She was one of the first Japanese women to emulate Western fashion in the 1920s by cutting her hair short. She designed her own house and was one of the first Japanese women both to own a car and a racehorse.^{[citation needed]}

In 1938, Yoshiya joined the Pen Butai (lit. "Pen Corps"), a government organisation of authors who travelled to the front during the Second Sino-Japanese War to write favourably of Japan's war efforts in China. She and Fumiko Hayashi were the only woman writers in the group.

Yoshiya lived in Kamakura, Kanagawa Prefecture during and after World War II. In 1962, she built a traditional wooden house with Japanese-style garden in a quiet area, which she willed to the city of Kamakura on her death, to be used to promote women's cultural and educational activities. She died at age 77 of colon cancer. Her house is now the Yoshiya Nobuko Memorial Museum, and preserves the study as she left it, with items such as handwritten manuscripts and favorite objects on display. The museum is open only twice a year, in early May and November, for three days each time. Her grave is at the temple of Kōtoku-in in Kamakura.

In January 1923, Yoshiya met Chiyo Monma (門馬 千代, Monma Chiyo) , a mathematics teacher at a girls' school in Tokyo. They would go on to have a romantic relationship for over 50 years. Unlike many Japanese public figures, she was not reticent about revealing details of her personal life through photographs, personal essays, and magazine interviews. In 1926, they established a collaborative working relationship of author and secretary. In 1957, Yoshiya adopted Monma as her daughter, the only legal way for lesbians to share property and make medical decisions for each other at the time. They both traveled together to Manchuria, Soviet Union, stayed for a year in Paris, and then returned via the United States to Japan from 1927–1928. In the late 1930s, they also visited the Dutch East Indies and French Indochina.

One of Yoshiya's early works, Hana monogatari ( 花物語 "Flower Tales", 1916–1924), a series of fifty-two tales of romantic friendships, became popular among female students. Most of the relationships presented in Flower Tales are about unrequited love, pining from afar, and/or have unhappy endings. These stories often depict female-female desire with a dreamy writing style.

Yaneura no nishojo ( 屋根裏の二處女 "Two Virgins in the Attic", 1919) is thought to be semi-autobiographical, and describes a female-female love experience between dormmates. In the last scene, the two girls decide to live together as a couple. This work criticizes a male-oriented society and presents a strong feminist attitude.