Seinen manga (青年漫画) are manga marketed to adolescent boys and men old enough to read kanji. In Japanese, the word "seinen" literally means "youth", but the term "seinen manga" is also used to describe the audience of comics like Weekly Manga Times and Weekly Manga Goraku which are aimed at men into their 50s. Seinen manga are distinguished from shōnen manga which are for younger boys, as well as the seijin-muke, or hentai, manga (成人向け漫画) which focus on sex, although some seinen manga like xxxHolic share some similarities with "shōnen" manga. Seinen manga can focus on action, politics, science fiction, fantasy, relationships, sports, or comedy and while they may contain sexual content (as well as other mature material), it remains predominantly more infrequent than in the seijin-muke manga. The female equivalent to seinen manga is josei manga.
Seinen manga have a wide variety of art styles and variation in subject matter. Examples of seinen series include: 20th Century Boys, Akira, Tokyo Ghoul, Berserk, Mushishi, Ghost in the Shell, Planetes, Maison Ikkoku, and the formerly shōnen manga JoJo's Bizarre Adventure.
A common way to tell if a manga is seinen is by looking at whether or not furigana is used over the original kanji text: if there are furigana on all kanji, the title is generally aimed at a younger audience. The title of the magazine it was published in is also an important indicator. Usually Japanese manga magazines with the word "young" in the title (Weekly Young Jump for instance) are seinen. There are also mixed shōnen/seinen magazines such as Gangan Powered and Comp Ace. Other popular seinen manga magazines include Young Magazine, Weekly Young Sunday, Big Comic Spirits, Business Jump, Ultra Jump, and Afternoon.
One of the earliest manga magazines published in Japan was a seinen manga: Weekly Manga Times, first released in 1956. It was aimed squarely at middle-aged men with erotic fiction and manga and tales of yakuza. It was only in 1959 that two of the main shōnen manga titles appeared, Weekly Shōnen Magazine and Weekly Shōnen Sunday. Then in 1967, the first of the magazines aimed at younger men appeared Weekly Manga Action which scored big hits with Lupin III and Lone Wolf and Cub, and later Crayon Shin-chan. Big Comic followed in 1968, perhaps best known for its series Golgo 13. 1972 saw the addition of Big Comic Original which featured Tsuribaka Nisshi about two older men who enjoy fishing which was made into a series of popular movies. In 1979, the publisher Shueisha known for Weekly Shonen Jump for boys, entered the seinen market with Weekly Young Jump. Many of the Young Jump series have been adapted into anime or live action TV programs, e.g. Elfen Lied, Gantz, Hen, Kirara, Liar Game, Oku-sama wa Joshi Kōsei and Zetman.
A list of the top Japanese seinen manga magazines by circulation in the timespan from 1 October 2009 to 30 September 2010.