The Gunners were crowned Premier League champions for the first time in 22 years after Pep Guardiola's side were held to a 1-1 draw at Bournemouth on Tuesday (Wednesday AEST).
It left Arsenal with an unassailable four-point lead at the top, with one round to play, and kicked off the celebrations in North London.
Mikel Arteta's side will formally be presented with the trophy on Sunday after their final match of the season at Crystal Palace.
They could still make it a historic double for the club as they chase their first Champions League title in the final against Paris Saint-Germain later this month.
The league title ended a six-year period without a trophy and is Arteta's second major honour in charge after the 2020 FA Cup victory.
Midfielder Declan Rice posted a picture on Instagram with his teammates with the caption "I told you all.. it's done."
Former boss Arsene Wenger, who led the team to their last title, in 2004, featured in a celebratory post from the Gunners on their X account.
He said: "You did it. Champions go on when others stop. This is your time. Now, go on and enjoy every moment."
Ex-England goalkeeper David Seaman, who made more than 400 appearances for Arsenal between 1990 and 2003, said on X: "Premier League champions!!! What a moment!!! What a season!!!!!!!! EPIC!!!!!!!!!! Longest (22 years and) three minutes of MY LIFE…"
Former Arsenal striker Alan Smith, a two-time title-winner, was thrilled to see his former club finally get over the line after several near misses in recent seasons.
"Brilliant, brilliant, fully deserved," he said on Sky Sports.
"Obviously, they've had their moments in the last few seasons where they've come second, but you deserve to win it if you finish top.
"They've had the best defence. They haven't had the best attack – you'd probably say City have got the best attack – but, as an overall unit, Mikel Arteta's done brilliantly well. I'm really pleased for my old club."
Martin Keown, a member of Wenger's three title-winning sides, posted on X: "Congratulations to this group for becoming champions! A beautiful moment. Come on the @Arsenal! Enjoy, rest and let's go and win our first champions league!"
Arsenal-supporting prime minister Sir Keir Starmer wrote on X: "22 long years for the Arsenal. But finally, we're back where we belong. Champions!"
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