Centre-back White has signed for the Gunners for a fee of £50m and signed a five-year deal.
The 23-year-old spent the 2019-20 Championship season on loan at Leeds and played every single minute of every league game as Marcelo Bielsa's Whites stormed to promotion as champions.
Leeds then made White their top target of the summer but Brighton refused to sell and insisted White was not for sale despite several big money bids of up to £30m.
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White stayed put and has since gone on to become an England international.
The defender's switch to Arsenal was announced on Friday afternoon, after which White took to his social media pages to post a photograph of himself holding a Gunners shirt along with the words: "My new home. Can't wait to get started."
The post received a whole host of replies from Whites players and also former Leeds left back Barry Douglas who put: "Yessss benji love it bro."
Luke Ayling went with a simple "congratulations mate" along with two hearts whilst Adam Forshaw also posted two hearts together with "smash it mate".
United's Bournemouth loanee Leif Davis, Morecambe loanee Alfie McCalmont and Blackpool's former Leeds defender Oli Casey were also amongst the first with Leeds connections to post their congratulations.
Whites skipper Liam Cooper, winger Ian Poveda and youngster Robbie Gotts also replied to salute the move whilst White's particularly close friend and former United team mate Kalvin Phillips was of course involved, sending three hearts.
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Thank you Laura Collins