Kim Kardashian and Kanye West's new mansion got spray-painted by mystery taggers -- freaking out neighbors and security guards -- but the homeowners themselves are totally chill.

The reason? We found out the Wests graffiti'd their own place!

Our Kardashian sources tell us the family got a bunch of calls Wednesday morning when people living next to the compound noticed the his and hers "I heart" paint job. We're told Kim calmed everyone down, because she and Kanye had gone to the house -- which is still under construction -- and did the tagging on Tuesday.

We know what you're thinking. Yes, they love themselves, but not that much. The house is getting re-plastered Thursday, so they decided to have some fun.