An unsettling situation for Nicole Kidman and Keith Urban ... cops say an intruder broke into their home.

Law enforcement sources tell TMZ ... Nicole and Keith are the latest A-listers to become crime victims, now that their Los Angeles-area home has been burglarized.

Our sources say Nicole and Keith were not home at the time, but one of their employees scared the person off.

We're told the incident happened over the weekend when someone smashed a glass window to gain entry into the famous couple's home.

We're told a member of Nicole and Keith's house staff came home and the intruder took off running when they heard the staffer coming in.

Unclear what, if anything, may have been stolen here ... out sources say when Nicole and Keith get back home they will have to take a look around to see if anything is missing.

So far, police have made no arrests but we're told the official investigation is ongoing.