TMZ has obtained the Timbaland 911 call, in which his mother-in-law desperately declares an emergency -- stating the rapper/producer was "tired of the stress" and by a cliff in a canyon.

TMZ broke the story, after receiving the call, the L.A. County Sheriff's Department dispatcher sent out a "possible suicide attempt" APB. A helicopter spotted Timbaland, deputies came, took him home and determined his life was not in danger.

The Sheriff's Department tells TMZ ... "Initial information provided to the Sheriff's dispatch suggested that Mosley [aka Timbaland] might have taken some sort of medication that would make finding him more urgent."