Emery moves to the Emirates Stadium after two years in charge of Paris Saint-Germain where he won one Ligue 1 title and swept the domestic cups.
Born in Spain, the 46 year old established himself as a dominant force in the La Liga with consecutive Champions League qualification with Valencia and also three consecutive Europa League titles with Sevilla.
Speaking on his appointment Arsenal chief executive Ivan Gazidis said: “Unai has an outstanding track record of success throughout his career, has developed some of the best young talent in Europe and plays an exciting, progressive style of football that fits Arsenal perfectly.
"His hard-working and passionate approach and his sense of values on and off the pitch make him the ideal person to take us forward.
“We conducted a confidential, wide-ranging and rigorous search involving extensive background references, data and video analysis, and personal meetings with all the candidates we shortlisted. All were interested in the position and we were unanimous in our choice of Unai to drive the next chapter of our history."
Speaking to the Arsenal website Emery stated that he was delighted with his appointment as the new boss for the Gunners.
He said, “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.”