Germany goalkeeper Bernd Leno has agreed to join Arsenal from Bayer Leverkusen for a reported 22m euros (£19.3m).
Leno, 26, has made more than 230 appearances for the Bundesliga side.
He has won six caps for Germany but was not included in their World Cup squad.
"Happy and proud to play for this great club Arsenal in the future! I'll do my best and I'm looking forward to the start of the new season as a Gunner," Leno tweeted.
Arsenal said the deal is "subject to the completion of regulatory processes".
"Bernd is a goalkeeper of high quality and experience," Arsenal manager Unai Emery said.
"He has been a top performer and regular number one goalkeeper for the past seven years."
A Leverkusen statement said Leno had signed a "long-term contract" with Arsenal.
Petr Cech and David Ospina are Arsenal's current first-team goalkeepers.
New manager Emery signed defender Stephan Lichtsteiner on a free transfer from Italian champions Juventus this month.
Leno is a 'great goalkeeper'
"I've enjoyed my time at Leverkusen from day one to now," said Leno. "I'm very grateful the club chose me to be the number one as a 19-year-old.
"After seven fantastic years, I'm now on my to another very exciting league. But I'm sure we'll meet each other often on the European stage in the future."
In 2011, Leno became the youngest goalkeeper to feature in the Champions League when he played against Chelsea aged 19 years and 193 days.
He made his Germany debut in 2016 and was part of the squad that won the 2017 Confederations Cup.
Leno was named in Germany's provisional 27-man squad for the World Cup in Russia, but was left out of the final 23.
Leverkusen sporting director Jonas Boldt described Leno as a "great goalkeeper".
He said: "Bernd has consistently performed well for us over the years. We wish him all the best in his future at Arsenal."
Bould stays as Lehmann leaves
In changes to the backroom staff at Arsenal, Steve Bould will continue as assistant manager, alongside Emery's long-time assistant Juan Carlos Carcedo.
Pablo Villanueva joins as first-team coach, while director of high performance Darren Burgess and goalkeeping coach Sal Bibbo retain their positions as Arsenal chief executive Ivan Gazidis looks for "continuity in a period of change".
Former Arsenal goalkeeper Jens Lehmann is among the coaching staff departing, along with Neil Banfield, Tony Colbert, Gerry Peyton, Boro Primorac and Colin Lewin.
Physiotherapists Andy Rolls and Ben Ashworth, osteopath Dr Philippe Boixel and travel manager Paul Johnson have also left.