The England international, 23, underwent a medical earlier today and will play for the Gunners for the next five seasons. Arsenal confirmed the deal in the early hours of Tuesday morning on their official website.
Manchester United allowed Welbeck to leave Old Trafford after striking a surprise deal for Colombia international Radamel Falcao, who has joined the Red Devils on loan for the season.
Welbeck wanted to leave Manchester United
Welbeck joined Manchester United’s youth academy at the age of 11 and made his senior debut in 2008. The Longsight-born striker is a popular figure at Old Trafford but made his decision to leave his boyhood club earlier this summer after failing to establish himself as the club’s main striker.
Welbeck was often deployed on the left flank by Sir Alex Ferguson and David Moyes, both of whom preferred to use Robin van Persie or Wayne Rooney as the team’s most advanced forward.
Van Gaal keen to sell Welbeck
United boss Louis van Gaal told Welbeck that he was free to leave the Red Devils in a face-to-face meeting last week, but the veteran Dutch coach was not expected to sanction a move to one of United’s top-four rivals.
Tottenham were determined to sign Welbeck, but the player was believed to be more keen on a move to Arsenal, who were in need of a new centre-forward with Olivier Giroud out until January having had surgery on his ankle.
Welbeck leaves Manchester United having scored 29 goals in 139 appearances for the Red Devils.