Sean Penn -- Secret Interview With El Chapo ... 'He Has Charisma'

El Chapo was one of the most wanted men in the world and Sean Penn knew exactly where to find him ... meeting with the drug lord for a long interview while he was on the run, and the actor clearly felt Chapo's star power.

Penn did the interview for "Rolling Stone" and carried out a secret mission to meet the fugitive in a Mexican jungle. The actor hopped on a charter plane in L.A., flew to Mexico, met El Chapo's son and took another plane deep into the jungle, where the 2 met.

During the interview, Penn was surrounded by more than 100 cartel troops. Chapo bragged he "supplies more heroin, methamphetamine, cocaine and marijuana than anyone in the world."

Penn asked Chapo about Donald Trump and his comments about Mexicans ... and the drug lord called Trump "Mi amigo."

And there's this ... Penn wrote of Chapo, "He has an indisputable charisma."

Penn's 7-hour interview -- conducted in October -- was a lynchpin in the capture of Chapo, according to one report, although it does not explain how ... it appears authorities may have learned of Penn's interview and used it to track down Chapo.

Penn wrote about El Chapo getting offers from Hollywood to do his life story, which appears to be the impetus for his decision to create a biopic. He actually got in touch with producers and actors, which was a key to his capture.