Welbeck signed for Arsenal for £16m on deadline day after spending his whole career at United, where he scored 29 goals in 142 appearances in all competitions.
The England striker says he has always followed Arsenal's progress closely, and feels he will be able to hit the ground running with the club.
"It's great to be a part of this club and it's a team that I've always watched in the Premier League," Welbeck told Arsenal's official website. "I've envisaged myself playing in this team before. For it to finally happen is very exciting.
Welbeck believes Arsenal are Premier League contenders this season, and sees their FA Cup triumph as a catalyst.
"Last year we got the FA Cup and I feel like it's time where we could really push on and try and challenge for the Premier League title."
The 23-year-old's transfer went through after the 11pm transfer deadline on Monday night, after Arsenal were granted an extension to complete the deal. Welbeck admitted that the deal had hit the buffers during the day, and spoke of his relief when ti was finally concluded.
The 13 players that have left Manchester United under Louis van Gaal
The 13 players that have left Manchester United under Louis van Gaal
1/13 Shinji Kagawa (Borussia Dortmund £6.3m)
The Japanese midfielder arrived at Old Trafford amid a sea of hope and expectation, but his time at Old Trafford will sadly be remembered as a failure. Kagawa established himself as one of the standout attacking midfielders in European football, helping Borussia Dortmund to consecutive Bundesliga titles between 2010 and 2012 before United came calling. Sir Alex Ferguson seemed uncertain on where Kagawa’s best position was, alternating him between his favoured central role and playing as a left-sided winger where he was largely anonymous. His torrid time in the Premier League came to an end on Sunday, as Dortmund took him back for around £10m less than they received two years ago.
2/13 Alexander Buttner (Dinamo Moscow, £5.6m)
Just when Buttner put in his best performance for United, he found himself out the door. His showing against Bayern Munich last season was arguably his finest in the red of United, and with Patrice Evra nearing the end of his contract, there was talk that the Dutchman could push on for a regular starting spot. However, Van Gaal’s arrival signalled the end of his two-year stay with United, as he clearly signalled his intention not to play under the former Netherlands manager that overlooked him for the World Cup.
3/13 Patrice Evra (Juventus, £2.5m)
Evra unusually agreed a one-year contract extension just over a month before his contract ran out only to leave the club two months later. The veteran left-back signed a new deal to keep him with the club until 2015, and looked to be in Van Gaal’s plans to help develop new signing Luke Shaw. That was until Italian champion Juventus lodged a £2.5m offer, and United decided to cash in on the Frenchman after eight years of loyal service.
4/13 Bebe (Benfica, £2.4m)
One of Sir Alex Ferguson’s biggest mistakes finally left United this summer after a dismal time in Manchester. Bebe arrived at United in 2010 for a rather worrying £7m even though Ferguson had never seen him play, and he quickly showed that he did not have the skills to cut it at Old Trafford. Just two appearances and three loan spells later, Bebe was offloaded to Benfica for less than half of what United paid for him. The less said about Bebe, the better.
5/13 Rio Ferdinand (QPR, free)
While Ferdinand technically left the club before Van Gaal arrived, you have to believe that the incoming manager would’ve instructed the club to tie him down to a new contract should he feature in his plans. Having spent 12 long and successful years with the club, Ferdinand was on the move, which came as a surprise given that United had already bode farewell to another veteran defender in Nemanja Vidic. The former England captain agreed a free transfer to join up once more with Harry Redknapp after agreeing to join QPR, having worked together at West Ham at the start of Ferdinand’s career.
6/13 Angelo Henriquez (Dinamo Zagreb, loan)
Henriquez is yet to make his United debut despite joining the club two years ago, and at 20 years old the belief is that he may have missed the boat if he is to break into the side. Having been sent on loan to Wigan and Real Zaragoza, Henriguez will spend this season with Dinamo Zagreb, and the likelihood is that he won’t be part of Van Gaal’s plans in the future.
7/13 Nani (Sporting Lisbon, loan)
The great hope who was tasked with replacing Cristiano Ronaldo never really delivered on his promise, as he ranged between the occasionally sublime and the regularly frustrating during his many performances for United. He looked to be on his way out of the club two seasons ago, only for David Moyes to arrive and promptly reward him with a five-year contract that still has four years left to run. Despite the lengthy deal, Nani was offered to his former club Sporting Lisbon, and will spend the season back in his homeland in an attempt to find some form.
8/13 Wilfried Zaha (Crystal Palace, loan)
United were quick to sign the promising Zaha after he impressed with Crystal Palace, but he has never really been given a chance to stamp his claim for first team recognition. Moyes sent him out on loan to Cardiff for the second half of last season, and he has been allowed to return to South London for this campaign in an attempt to rediscover the form that saw many mark him out as an England star of the future.
9/13 Javier Hernandez (Real Madrid, loan)
The eternal super-sub has departed for the European champions to become, well, a super-sub. It’s highly unlikely that Hernandez will be able to usurp the likes of Karim Benzema, Cristiano Ronaldo and Gareth Bale, and he looks likely to be used by Carlo Ancelotti as cover for the big-three alongside Jese Rodriguez once he returns from a long-term knee injury.
10/13 Tom Lawrence (Leicester, £1m)
The 20-year-old made his sole appearance for United at the end of last season after interim manager Ryan Giggs handed him his first Premier League start in the 3-1 win over Hull – he was later substituted for the United legend’s final appearance before retirement. Having spent loan spells with Carlisle United and Yeovil Town during the last year, he completed a £1m move to Premier League newcomers Leicester City on deadline day.
11/13 Danny Welbeck (Arsenal, £16m)
A somewhat surprise departure on the final day of the transfer window saw Welbeck head to Premier League rivals Arsenal for £16m in a deal that was not announced until nearly 1am this morning. Welbeck has always struggled to lock himself into the starting line-up under both Ferguson and Moyes, and while he has made three appearances under Van Gaal he did not start a league game for United under the Dutchman. Welbeck will hope a solid run in the Arsenal side in the absence of Olivier Giroud will help establish himself at his new club.
12/13 Nick Powell (Leicester, loan)
Powell joined United as a highly-rated teenager from Crewe Alexander tipped for a big future, and spent last season with Wigan where he impressed in the Championship. His reward is a chance to show he can cut it in the Premier League, and his addition to Leicester could be one of the loan signings of the summer if it pays off, such is his talent. While he may not feature in Van Gaal’s plans just yet, regulars at the King Power Stadium will be licking their lips in anticipation at seeing what he can offer to Nigel Pearson’s side.
13/13 Michael Keane (Burnley, loan)
Keane is another who has been rewarded for a long spell in the championship with a loan move to a Premier League side. He’s featured for Leicester, Derby and Blackburn in recent years having made just one appearance for United, and Burnley will hope he can help them to an unlikely Premier League survival given they are the bookies favourites to go down at the end of the season.
"It went right down to the wire in the end," he said. "It's difficult to say how I felt at the [different] times of each day because the deal was on and then it was off but at the end of the day I'm an Arsenal player and I couldn't be any happier at the moment.
His former team-mate at United, Rio Ferdinand, claimed that Welbeck will "flourish and explode" at Arsenal.
"Welbeck is a top signing for Arsenal," Ferdinand wrote on Twitter. "If he gets that trust to be No 1 striker at AFC he will flourish and explode."
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