Everyone thought Machine Gun Kelly and Megan Fox were over as a couple -- but the two of them were just hanging out for his 34th birthday ... and MGK posted the evidence.
Kelly threw up a carousel of pics Wednesday on his IG -- which captured a ton of moments from his birthday party earlier this week, which looked like a star-studded soiree featuring the likes of Post Malone, Tiffany Haddish, Evan Ross, Mod Sun, Amber Rose and others.