Williams enjoyed spells at West Ham and Ipswich before joining Bristol City in 2008, but has started just two league games this season.
He told the club website: "It's good to be back and get some games. I also hope we can pick up the right results."
The Welshman continued: "The manager here has done a terrific job. Now hopefully we can push right up the table and finish as high as possible."
Source: BBC Sport
Source: BBC Sport