The 22-year-old, who won five England Under 21s caps under Reds boss Stuart Pearce, made 20 appearances on loan at Brighton earlier this season, scoring twice.
He has made a number of Premier League appearances for Villa and will be eligible for selection against Sheffield Wednesday, where he had a brief loan spell last season.
Gardner follows in the footsteps of Todd Kane, who arrived at The City Ground on loan from Chelsea on Thursday.
Both signings possible thanks to the £250,000 Sky Bet Transfer Fund which was won by Nottingham Forest fan Shaun Lander. For your chance to win your club the next Transfer Fund, sign up at skybet.com/win
Read more about Todd Kane's arrival here
For your chance to help Forest win the next Transfer Fund, sign up at skybet.com/win
Gary's player sponsorship
is now available for the second half of the Sky Bet Championship season, priced at £477
+ VAT. For more information call the commercial team on 0115 982 4450.