Someone broke into RIHANNA's home in the Hollywood Hills and STAYED THE NIGHT.
Rihanna was NOT home at the time . . . and the police were alerted when the security company got suspicious that her alarm had been tampered with.
When they showed up, they found a 26-year-old guy, and they arrested him for felony stalking. It's unclear if he'll face additional charges. TMZ says he resisted arrest, and had to be TASED. He's being held on $150,000 bail. (TMZ)