The Spaniard’s contract at Brentford is due to expire in a year’s time, but he will sign an extension before leaving on loan.
Raya underwent a medical with Arsenal on Thursday and the club hope to officially sign him before they kick off their top-flight season at home to Nottingham Forest on Saturday.
Under current Premier League rules, the Gunners have to register the signing before midday on Friday for Raya to be included in their matchday squad.
Arsenal have moved for the Brentford goalkeeper after selling former No2 Matt Turner to Nottingham Forest this week in a deal that could be worth £10m.
Raya’s arrival will strengthen Arsenal’s options in goal and provide support and competition for current No1 Aaron Ramsdale.
The England international started all of Arsenal’s Premier League games last season and has said he will relish a new rival for the gloves.
“Bring it on,” Ramsdale told ITV Sport when asked about Raya’s expected arrival. “Nothing comes easy in football, but you need to move along and need to adapt as well yourself.
“I’ve done it to other people when I’ve moved to clubs, so I’m not going to be thinking that it’s never going to happen to me. If it happens, it happens.”
