Nicole Kidman And Keith Urban Separated, Keith's Decision

Nicole Kidman and Keith Urban have separated ... TMZ has learned.

Multiple sources with direct knowledge tell TMZ ... the couple has been living apart "since the beginning of summer."

We're told Nicole has been taking care of their 2 children and, "holding the family together through this difficult time since Keith has been gone."

As for why, we're told it's one-sided ... Nicole did not want the separation and has been trying to save the marriage.

One source said, "Keith has acquired his own residence in Nashville and has moved out of their family home," which is also in Nashville.

As for whether the couple will divorce ... to be determined.