Chile forward Sanchez, 29, who almost joined Manchester City last summer signed a four-and-a-half-year deal.
Speaking about his transfer, Alexis Sanchez said: “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.”
