Gardner is reunited with Forest boss Stuart Pearce, who handed the 22-year-old five caps for England Under-21's during his time in charge
He is the second signing Forest have made using their £250,000 Sky Bet Transfer Fund after also capturing Chelsea defender Todd Kane on loan from Chelsea this week
Gardner has made just five first-team starts for Villa and has just returned from a loan spell in the Championship at Brighton, scoring twice in 20 appearances
Pearce said: "We are delighted Gary has agreed to join us until the end of the season
His ability and character will be essential between now and the end of the season."
Gardner will be available for Saturday's home clash with Sheffield Wednesday, where he had a brief loan spell last season
He said: "It's a great club and I'm relishing the opportunity
I can't wait to get going and help the club in their pursuit of promotion."
Source : PA