R&B SINGER CHRIS BROWN PROPOSES TO HIS GF . . . THEY'RE GETTING MARRIED!!!

According to a reliable source Chris Brown PROPOSED to Karrauche over the weekend . . . and she said YES!! The snitch explained, "Chris asked her to marry her . .. . it was very [spur of the moment]. It was over the phone and he doesn't even have a ring for her yet. But she said yes."

The insider tells MediaTakeOut.com that couple is trying to keep everything on the hush-hush for now . . . until AFTER Chris returns from touring.

Well, Chris seems to be trying to settle down and turn himself around. So we GOTTA support that . . .