INTRUDER ARRESTED AT RIHANNA'S HOUSE!

A man was arrested at Rihanna's Southern California home in the Pacific Palisades ... after neighbors saw the guy snooping around the house and apprehended him on the spot.

Law enforcement sources tell TMZ ... the suspect has told police someone emailed him instructions on how to get into the home ... so he rolled over to the property and followed the directions.

TMZ was told the instructions worked ... because the man was able to get inside the home ... where he allegedly snooped around for a while before neighbors noticed something was up.

TMZ sources say ... neighbors went over to the home and confronted the man -- and eventually detained him when they realized he didn't belong there. Police were called to the scene and took the man into custody.

The man is currently being investigated for burglary.

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