McLaughlin joined Forest in January from Derry City, but the 23-year-old has yet to make his debut for the Championship club.
He will now have the chance of first-team experience at Ashton Gate and former Forest boss Sean O'Driscoll is happy to have added the Irishman to his squad.
O'Driscoll told the club's official website: "Stephen's a young Irish winger who can play both sides, and someone who impressed when on trial at Forest during my time there and did enough to earn a contract.
"He's well-balanced, technically sound and got an eye for a goal. He's someone we think will add versatility and depth to the squad and that we can help to continue develop during his stay with us.
"We're very grateful to Forest for allowing us to take Stephen on loan."