Kim Kardashian's Sex Tape Master Almost Perishes in Fire!!!

Oh the humanity! The unedited master of Kim Kardashian's sex tape -- Kim K Superstar -- almost burned up over the weekend in a raging fire at Vivid Entertainment ... TMZ has learned.

The master -- think of it as the Mona Lisa of sex tapes -- was secured in a safe inside Vivid honcho Steve Hirsch's office. When the blaze erupted Saturday night ... Hirsch was miles away at an L.A. Clippers game.

Hirsch got the 911 call and bailed immediately, because the safe not only contains Kim's tape but every unedited master of every celebrity sex tape in Vivid's stable, including the ones starring Kendra Wilkinson, Pam and Tommy Lee, Jimi Hendrix, Vince Neil, Tom Sizemore, and Chyna.

Also in the vault -- several celebrity sex tapes that have never seen the light of day.

Fear not ... because Hirsch made it just in the nick of time. The safe was singed but the contents were intact.