https://www.cnet.com/news/what-are-skrulls-aliens-of-captain-marvel-2019/

The Skrulls first appeared in Fantastic Four #2.

Created by Stan Lee and Jack Kirby, the Skrulls first showed up in 1962's Fantastic Four #2. Preparing for an invasion of Earth, they believe the Fantastic Four stand in their way, so four scouts impersonate the hero team and try to turn the public against them.