Monthly Sunday Gene-X (Japanese: 月刊サンデーGENE-X, Hepburn: Gekkan Sandē Jenekkusu), often abbreviated as Sunday GX (サンデーGX), is a seinen manga magazine published by Shogakukan.

Like many other manga magazines, it is an "anthology magazine", with each issue featuring new chapters of several manga series.

The series are also published in tankōbon form under the Sunday GX Comics imprint.

The magazine's title, Monthly Sunday Gene-X, refers to its mission as a manga magazine for Generation X.

[4] Shogakukan also publishes manga series previously featured in Sunday GX as paperback tankōbon (compilation volumes) under the imprint Sunday GX Comics.