and the rest of the members of No Doubt are getting together again after a good long while -- and they're it in the desert ... headlining Coachella, no less.

The lineup for the annual music festival just dropped, and while there are 3 big acts slated to perform Fri-Sun on 2 different weekends ... it looks like Gwen and co. will be the real talent -- 'cause they're being listed as a general, all-around headliner ... with no specific dates.

Goldenvoice has performing on Friday April 12th and 19th; will handle headlining duties on Saturday April 13th and 20th; and will do Sunday.

But, take a look at the bottom of this poster, it just reads ... "And ... No Doubt." Again, no clarity on what that means or which day the band might do their thing -- it's a mystery.

Funny enough, ND actually teased this about an hour before Coachella dropped the lineup -- teasing the fact they were itching to get together again and "do a show." It's a fun, somewhat produced clip that features Gwen, , Tom Dumont and Adrian Young hopping onto a group chat and then a Zoom .

.. where they kicked around the idea of performing.

As it turns out, they're gonna be making a splash with their big comeback gig -- hitting the stage on possibly the biggest platform in music ... performing in front of thousands of people.

No Doubt hasn't performed as a group in a while -- in fact, the last time they hit the stage together in an official capacity was in 2015 during that year's Global Citizen Earth Day Concert in D.C. Since then, they haven't really rocked out as a unit.

Now, fans will get a chance to see 'em live .

.. and get underneath it all in person. Sweet!