The 19-year-old, who is yet to start a Premier League match for Villa, recently signed a new four-year deal with the club.
Grealish impressed during a loan spell with Forest's neighbours Notts County last season.
Recent reports have suggested that Chelsea and Manchester City are interested in signing the highly-rated youngster.
Forest manager Stuart Pearce is keen to use the loan market to bolster his squad and has identified Grealish as a target, according to The Mirror.
Grealish has made five appearances for Villa this season.