Wenger's replacement is the 46-year-old Spanish coach Emery, who left Paris Saint-Germain earlier this summer after two years in the French capital, winning the domestic treble this season.
“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," said Emery.
"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."
Emery's most notable body of work was winning three successive Europa League titles as Sevilla coach between 2014 and 2016. He began his coaching career at Lorca Deportiva in 2005 while also coaching Almeria, Valencia and Spartak Moscow.
Wenger's final season in charge ended in disappointment with Arsenal finishing sixth in the Premier League -- missing out on Champions League qualification for the second season in a row.
Emery had strengthened speculation he would take over as Arsenal's new manager after a photo appeared on his official website https://unai-emery.com/en announcing him as the Premier League club's coach.
He is infamously remembered for PSG's 6-1 defeat at Barcelona last season in the Champions League last 16 that saw PSG squander a 4-0 lead from the first leg to go out of Europe in humiliating fashion.
Despite spending £198 million to break the world transfer record to land Neymar from Barcelona, PSG suffered more disappointment in the Champions League last 16 this term as they lost 3-1 away and 2-1 at home against Real Madrid.
Arsenal apparently opted against appointing former player Mikel Arteta as their next manager due to his lack of experience.
Arsenal majority shareholder Stan Kroenke and chief executive Ivan Gazidis apparently decided that appointing former the Gunners midfielder would be a risk because he lacks managerial experience at the top level.
The 36-year-old Spaniard now seems likely to continue in his assistant manager's role alongside Pep Guardiola at Manchester City.
“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," said Gazidis. "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."