Breaking transfer news: Villa secure loan deal for Chelsea ace
The 24-year-old full back has played in 56 matches in all competitions for Chelsea, including the 2012 Champions League final victory over Bayern Munich in the Allianz Arena.
He has represented England at every level from U17s through to the senior side, making his full England debut against Italy in 2012.
He also represented Great Britain at the London Olympics in 2012.
Manager Paul Lambert said: "Ryan brings a lot of big-game experience, not only in the Barclays Premier League but even a Champions League final which Chelsea won, so he'll be really good for us.
"The way he plays the game and as a person, too, he'll fit in here great and it will be good for him also to be playing games. He has real enthusiasm for the game and he's looking forward to playing here.
"We're grateful to Chelsea for allowing him to come here on loan and we know he'll be really good to work with."
Bertrand said: "It's a fantastic opportunity for me to come here. Aston Villa is a fantastic club with a massive fanbase and a great history. To get this chance to come here and play some games will be a really good step for me.
"Whenever I've played for Chelsea here at Villa Park the fans have been fantastic and have always created a great atmosphere. The pitch, too, has always been great, including when we played in the Community Shield here against Manchester City, and I'm looking forward to playing on it more regularly until the end of the season.
"I've had to adjust many times in my career having played under several managers, so I know I can settle in here quickly and I'm looking forward to being able to contribute to the team.
"I'm focussed on continuing to progress and helping the team here to do that, too. We have a lot of young, talented players here with some experienced heads as well, they want to express themselves and I hope I can add to that and add my experience in a productive way.
"This is a really traditional English club, a family club as well and you get the feeling that everyone really knows one another, so that side's not been lost either.
"Knowing some of the lads here, too, such as Fabian Delph, Marc Albrighton and a few others will really help, too, and I couldn't be more looking forward to playing my part here."
Born in Southwark, London, Bertrand began his youth career at Gillingham before he moved to Chelsea in 2005 as a 16-year-old.
He has enjoyed several loan spells, including at Bournemouth, Oldham Athletic, Norwich City, Reading and Nottingham Forest.
He made his debut for Chelsea in April 2011 in a 3-1 win over Birmingham City at Stamford Bridge.
Watch out for an exclusive interview with Bertrand soon on AVTV.