Monthly Shōnen SundayMonthly Shōnen Sunday.

Monthly Shōnen Sunday (Japanese: 月刊少年サンデー, Hepburn: Gekkan Shōnen Sandē), alternately known as Gessan (ゲッサン) (a portmanteau of "Gekkan" and "Sandē" from its full Japanese title), is a monthly shōnen manga magazine published in Japan by Shogakukan since May 12, 2009 (the June 2009 issue). The magazine was announced in February 2009, with Hayashi Masato, at that time editor of Weekly Shōnen Sunday, editing the monthly magazine as well. Manga artists who debuted new series or stories in the magazine include Yellow Tanabe, Mitsuru Adachi, and Kiyohiko Azuma.