Susan Sarandon referred to Pope Benedict XVI as a Nazi over the weekend – not just once, but twice.

During an interview at the Hamptons Film Festival, Sarandon was talking about sending the pope a copy of the book, “Dead Man Walking,” when she clarified ... “The last one [Pope John Paul II], not this Nazi one we have now.”

When interviewer Bob Balaban expressed disapproval, Sarandon reportedly said the Nazi comment AGAIN -- drawing laughter from the audience.

The Pope's PR people acknowledged that Benedict WAS a member of the Hitler Youth as a boy, a requirement at the time for German boys his age -- but the rep insists he had no "active participation" in the group.