Paris Jackson -- Left Suicide Note, Cut Arm with Meat Cleaver

Paris Jackson left a suicide note and then cut her arm with a meat cleaver ... TMZ has learned.

Sources with an intimate knowledge of the situation tell TMZ ... Michael Jackson's daughter called a suicide hotline and the person on the other end was alarmed enough to call 911.

Our sources say in addition to cutting her right forearm, Paris had taken a large number of Motrin pills.

We're told once Paris was taken by stretcher to an ambulance and then transported to a nearby hospital, she was placed under a 5150 psychiatric hold for 72 hours.

She received "numerous stitches" for the cut.

As for the suicide note ... we do not know what she wrote.

TMZ broke the story ... officials first responded to Paris' home in Calabasas around 1:30 AM Wednesday morning.