Brad Pitt is a hero onscreen and to his six kids -- but the Hollywood hunk really became a lifesaver in Venice!

As a sea of paparazzi swarmed Brad at the Venice Film Festival, a young autograph-seeker jumped off a boat, tripped -- and almost fell in the watery canal!

Brad grabbed the kid and pulled him to safety -- then signed an autograph and dashed off into the limelight. Curtain, please.

Click on an image to view the Brad & Angelina photo gallery!