Barry joins Stockport on a season-long loan.
The youngster returns to Stockport after helping them to the League Two title last term, scoring nine times in 20 appearances.
Barry has penned a new Villa contract ahead of the loan switch.
Stockport boss Dave Challinor said: “It’s brilliant news that Louie will be back with us as we venture into League One. We’ve been pretty open with our desire to make this happen but understood we had to be patient, but it’s finally done.
“Louie had a huge impact in the early part of last season and it was great for him to come back and be able to not only finish the job, but enjoy the celebrations of being League Two Champions. We are so excited to see Louie back at 100% fitness and have a similar impact on a higher division.
“Aston Villa have been fantastic with us and maybe the most important factor was Louie’s desire to come back here, despite lots of interest from other clubs. He’s fit, has played minutes and the supporters will hopefully see him back in a County shirt this weekend.”