-- the ex-Stanford swimmer convicted of rape --- has been placed in protective custody while serving his sentence at Santa Clara County Jail ... to keep him safe from inmates who might harm him.
We spoke to a rep for the Santa Clara County Sheriff's Office who confirmed to TMZ Sports Turner is being held in an area away from the general inmate population, and will have a deputy escort whenever he moves around the grounds.
He will be exposed to other inmates -- but only ones in "protective custody" -- which include people convicted of sexual assault, LGBT inmates and gang dropouts.