Denise Russo, famous for appearing on VH1’s “The X-Life,” Died from a lethal combination of two of the most powerful drugs on the streets … TMZ has learned.

According to the San Diego County Medical Examiner, Denise died from the toxic effects of fentanyl and methamphetamine in what’s being ruled an accidental overdose.

We broke the story … Denise was found unresponsive on the floor of a friend’s home in San Diego back in March and was pronounced dead.

Police said drug paraphernalia was found at the scene, and the medical examiner notes the same thing … saying paramedics arrived and performed “aggressive attempts at resuscitation” on the 44-year-old.

Denise was featured on the 2011 reality show, which followed the lives of extreme sports athletes and their partners … she was dating professional skateboarder Pierre-Luc Gagnon at the time. Denise and Pierre-Luc had a son together, but had since broken up.