Alexis Sanchez has completed his transfer to Manchester United with Henrikh Mkhitaryan moving in the opposite direction to Arsenal.
The 29-year-old Chile international forward, Sanchez, who almost joined Manchester City in the summer before the deal broke down late in the transfer window, has penned a four-and-a-half year deal at Old Trafford.
Sanchez, who scored 80 goals in 165 appearances during his time at the Emirates Stadium, will wear the famous number seven shirt at United.
On completion of the deal, the former Barcelona man told the United official website: "I am thrilled to be joining the biggest club in the world. I have spent three-and-a-half wonderful years at Arsenal and I bring with me very positive memories of that great club and its fans.
"The chance to play in this historic stadium and to work with Jose Mourinho was something I could not turn down.
"I am very proud to be the first Chilean player ever to play for United's first team and I hope I can show our fans all around the world why the club wanted to bring me here."
Meanwhile, 29-year-old Armenia international, Mkhitaryan, is delighted to join Arsenal on a three-and-a-half-year deal after scoring 13 goals in 63 appearances for United since joining from Borussia Dortmund for £26.3million in July 2016.
"I'm very happy that we could finish this deal and I'm very happy to be here," he said. "It's a dream come true because I've always dreamed of playing for Arsenal.
"Now that I'm here, I’ll do my best for this club to create history."
United are 6/4 to win the Premier League without Manchester City, while Arsenal are priced at 11/2 to secure a top-four finish.