Shōjo manga (少女漫画; lit. 'girls' comics', also romanized as shojo or shoujo) is an editorial category of Japanese comics targeting an audience of adolescent girls and young adult women. It is, along with shōnen manga (targeting adolescent boys), seinen manga (targeting young adult and adult men), and josei manga (targeting adult women), one of the primary editorial categories of manga. Shōjo manga is traditionally published in dedicated manga magazines, which often specialize in a particular readership age range or narrative genre.

Shōjo manga originated from Japanese girls' culture at the turn of the twentieth century, primarily shōjo shōsetsu (girls' prose novels) and jojōga (lyrical paintings). The earliest shōjo manga was published in general magazines aimed at teenagers in the early 1900s and began a period of creative development in the 1950s as it began to formalize as a distinct category of manga. While the category was initially dominated by male manga artists, the emergence and eventual dominance of female artists beginning in the 1960s and 1970s led to significant creative innovation and the development of more graphically and thematically complex stories. Since the 1980s, the category has developed stylistically while simultaneously branching into different and overlapping subgenres.

Strictly speaking, shōjo manga does not refer to a specific style or a genre but rather indicates a target demographic. While certain aesthetic, visual, and narrative conventions are associated with shōjo manga, these conventions have changed and evolved over time, and none are strictly exclusive to shōjo manga. Nonetheless, several concepts and themes have come to be typically associated with shōjo manga, both visual (non-rigid panel layouts, highly detailed eyes) and narrative (a focus on human relations and emotions; characters that defy traditional roles and stereotypes surrounding gender and sexuality; depictions of supernatural and paranormal subjects).

The Japanese word shōjo (少女) translates literally to "girl", but in common Japanese usage girls are generally referred to as onna no ko (女の子) and rarely as shōjo. Rather, the term shōjo is used to designate a social category that emerged during the Meiji era (1868–1912) of girls and young women at the age between childhood and marriage. Generally this referred to school-aged adolescents, with whom an image of "innocence, purity and cuteness" was associated; this contrasted the moga ("modern girl", young unmarried working women), with whom a more self-determined and sexualized image was associated. Shōjo continued to be associated with an image of youth and innocence after the end of the Meiji era, but took on a strong consumerist connotation beginning in the 1980s as it developed into a distinct marketing category for girls; the gyaru (ギャル) also replaced the moga as the archetypical independent woman during this period.

Strictly speaking, shōjo manga does not refer to a specific style or a genre, but rather indicates a target demographic. The Japanese manga market is segmented by target readership, with the major categories divided by gender (shōjo for girls, shōnen for boys) and by age (josei for women, seinen for men). Thus, shōjo manga is typically defined as manga marketed to an audience of adolescent girls and young adult women, though shōjo manga is also read by men and older women.

Shōjo manga is traditionally published in dedicated manga magazines that are directed at a readership of shōjo, an audience that emerged in the early 20th century and which has grown and diversified over time. While the style and tone of the stories published in these magazines varies across publications and decades, an invariant characteristic of shōjo manga has been a focus on human relations and the emotions that accompany them. Some critics, such as Kyoto International Manga Museum curator Kayoko Kuramochi and academic Masuko Honda [ja], emphasize certain graphic elements when attempting to define shōjo manga: the imaginative use of flowers, ribbons, fluttering dresses, girls with large sparkling eyes, and words that string across the page, which Honda describes using the onomatopoeia hirahira. This definition accounts for works that exist outside the boundaries of traditional shōjo magazine publishing but which nonetheless are perceived as shōjo, such as works published on the Internet.

As the Japanese publishing industry boomed during the Meiji era, new magazines aimed at a teenage audience began to emerge, referred to as shōnen. While these magazines were ostensibly unisex, in practice the editorial content of these magazines largely concerned topics that were of interest to boys. Faced with growing demand for magazines aimed at girls, the first shōjo magazines were published, and shōnen magazines came to target boys exclusively. The first exclusively shōjo magazine was Shōjo-kai [ja], first published in 1902. This was followed by Shōjo Sekai in 1906, Shōjo no Tomo in 1908, Shōjo Gahō in 1912, and Shōjo Club in 1923. These magazines focused primarily on shōjo shōsetsu (lit. "girls' novel", a term for illustrated novels and poems aimed at an audience of girls) and only incidentally on manga.

Shōjo shōsetsu nevertheless played an important role in establishing a shōjo culture, and laid the foundations for what would become the major recurrent themes of shōjo manga through their focus on stories of love and friendship. Among the most significant authors of this era was Nobuko Yoshiya, a major figure in the Class S genre whose novels such as Hana Monogatari centered on romantic friendships between girls and women. The visual conventions of shōjo manga were also heavily influenced by the illustrations published in these magazines, with works by illustrators Yumeji Takehisa, Jun'ichi Nakahara, and Kashō Takabatake [ja] featuring female figures with slender bodies, fashionable clothing, and large eyes. Japanese artists who studied in France at the time were influenced by the methods of expression of Art Nouveau and early pin-up artists.