He replaces Tim Sherwood, who was sacked last week after only eight months in charge following Villa's miserable start to the season, having narrowly escaped the drop last term.
Former Arsenal midfielder Garde said he was ready for "the difficult task" of trying to revive the seven-times English champions.
"It is an unbelievable honour to be the manager of such an illustrious football club," Garde told Villa's website (www.avfc.co.uk).
"I've had extremely positive meetings with both the owner, Randy Lerner, and chief executive Tom Fox. They have ambitious plans for the club and I'm excited that they have turned to me to help them realise them.
"Obviously we have a difficult task in front of us but I'm looking forward to the challenge with the support of everyone who loves Aston Villa."
Garde will be at White Hart Lane but not in charge of the team later on Monday when Villa take on Tottenham Hotspur.
Victory would lift them off the bottom of the table.
Villa were hit badly by the sales of players such as striker Christian Benteke to Liverpool and midfielder Fabian Delph to Manchester City in the transfer window, while new recruits such as Jordan Ayew and Adama Traore have so far struggled.
They have four points from 10 matches.
Garde has been taking a break since leaving Lyon last year, having taken the side to the French Cup in 2012.
American owner Lerner admitted Villa had fallen "way behind" but said Garde offered "ideas, honesty, humour and a steely sense of what it will take" for Aston Villa to climb the table.
"We recruited aggressively this past summer, and it is our responsibility to now harvest this talent rather than buckle under pressure and criticism -- we are better than that," Lerner added.
FIFTH MANAGER
Garde, who played for Arsenal from 1996-99, was an assistant coach at Lyon from 2003, helping them win successive Ligue 1 titles. As the club's manager he won the 2012 French Cup.
He becomes Villa's fifth full-time manager in five years since the successful Martin O'Neill, who finished in the top six for three straight seasons but quit after disagreeing with Lerner about the club's future direction.
One of the founder members of England's Football League in 1888, Villa were champions six times by 1910, but have won the title only once since.
That success, in 1981, was followed by a stunning European Cup triumph, with Villa beating Bayern Munich in the 1982 final.
(Editing by Ken Ferris and Stephen Wood)
Share
