Emery, 46, will take over from Arsene Wenger after departing the Ligue 1 club this month after his contract expired.
Former Everton and Arsenal player Mikel Arteta seemed destined for the role before an eleventh-hour decision by the board to opt – unanimously – for Emery.
Emery told the club website: “I am thrilled to be joining one of the great clubs in the game.
“Arsenal is known and loved throughout the world for its style of play, its commitment to young players, the fantastic stadium, the way the club is run. I’m very excited to be given the responsibility to start this important new chapter in Arsenal’s history.
“I have met Stan and Josh Kroenke and it’s clear they have great ambitions for the club and are committed to bringing future success.
“I’m excited about what we can do together and I look forward to giving everyone who loves Arsenal some special moments and memories.”
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