Paris Hilton and Chris Zylka Say They Have a Prenup

Paris Hilton insists when she says "I do" to Chris Zylka it's gonna be forever, but just in case ... they have a prenup.

We got Paris and Chris Thursday at LAX, and we asked them to settle it once and for all ... prenup or no prenup. After all, Paris' parents were split on whether she should get one.

Chris starts out ... something about gentlemen who marry rich ladies should not be askin' for a prenup. That's what you call a truism. But then he spills the truth.