The Gunners confirmed the news via Twitter on Wednesday:
German outlet Kicker (via German football writer Stefan Bienkowski) reported the final fee at €45 million (£34.2 million):
Manager Arsene Wenger has spent big, but he may finally have the dominant presence in central midfield he's missed since the days of Patrick Vieira.
The French manager explained that the Gunners have had their eye on Xhaka for some time, per Arsenal:
[Xhaka] is an exciting young player, already with good Champions League and Bundesliga experience.
We have been watching him for a long time now and he is a player who will add quality to our squad. We wish [Xhaka] a good Euro 2016 with Switzerland and look forward to welcoming him to Arsenal ahead of next season.
Meanwhile, the FC Basel youth graduate expressed his excitement at joining the north London outfit, per Arsenal: "I’m very proud to be joining Arsenal. I cannot wait to move to London, represent this special club and play in the Premier League. I will give everything to help Arsenal win trophies and make the fans happy."
Bleacher Report UK welcomed the talented midfielder to the Premier League upon the announcement:
Pairing Xhaka with Cazorla would give the Gunners a natural blend of physicality and technical quality. Per Wheatley, Wenger could swap the Spain international for French destroyer Francis Coquelin "in the Gunners' most difficult games."
But Xhaka's best fit could actually be alongside January signing Mohamed Elneny—as the duo could arguably be the most balanced central-midfield pairing Wenger could deploy.
Xhaka and Elneny would offer tenacity, energy and composure on the ball. They'd give Arsenal the strong base they need to let Wenger's many forward-thinking players flourish.
Whoever plays alongside him, Xhaka's combination of destructive power and intelligent passing will be key to Arsenal's success at the heart of midfield.
Per Match of the Day's Gary Lineker, Xhaka could play a key role for the Gunners next season as they go in search of their first Premier League title since 2004, while his name is something of a gift for the headline writers among the British press:
The 23-year-old is a rugged ball-winner who leaves no wasted motion when scrapping for the ball, per Squawka Dave:
But his aggression can sometimes get the better of him—as evidenced by his three red cards in the Bundesliga during the recently concluded campaign.
Xhaka is also a cultured passer who smartly picks out runners between the lines. He is blessed with an excellent left foot and specialises in stroking long passes into wide areas.
He's also a natural boss on the pitch, having secured the Gladbach captaincy at a young age. Xhaka has tested himself at the highest level, having earned UEFA Champions League experience both during his time in the Bundesliga and with Basel.
Yet his former national team boss Ottmar Hitzfeld offered a different comparison. He instead viewed Xhaka as a younger version of Manchester United's Bastian Schweinsteiger, per Patrick Surlis of Sky Sports.
Whichever comparison you favour, Xhaka's influence is noticeable in most games. His knack for making himself both a conductor and destroyer in the middle will be appreciated in north London.
With Elneny set for Africa Cup of Nations duty next year, and Arsenal saying goodbye to veterans Tomas Rosicky, Mathieu Flamini and Mikel Arteta, Wenger has moved swiftly to shore up a key area of his squad.
Expect Xhaka to quickly make the grade with his new club.