Sad news in Springfield ... "Simpsons" creator Matt Groening's mourning the loss of his beloved 94-year-old mother Margaret ... as in Marge ... as in Marge Simpson.

In fact, Margaret's obituary has surfaced online ... and it mentions several members of the Groening family -- including Homer, Lisa, Maggie and Patty.

FYI -- Margaret's maiden name was Wiggum.

It's not new "news" that Matt named several of his characters after family members ... just interesting to see it in print.

As for Matt's mom ... she died peacefully in her sleep on April 22. Mmmmmmm peace.