The Turkey international, 28, will arrive on loan from Manchester United, where he has barely featured in the Premier League or domestic cups since joining three years ago from Fenerbahçe.
In that time he has made just 17 official appearances, 10 of them in the Premier League. Bayindir joined United from the Turkish club in 2023 for a fee of around €5m, arriving with hopes of challenging for the number one shirt but ending up almost exclusively as back-up, a role that has left him short of regular football heading into the new season.
Before joining Manchester United, Bayindir made 166 appearances across spells with Ankaragücü and Fenerbahçe, keeping 53 clean sheets, and was the first Turkish player to sign for the Old Trafford club when he arrived in 2023.
Giráldez has given the move his approval and has already spoken with the player himself, with the coach keen to raise the level of competition in goal behind Ionut Radu, who joined Celta Vigo last summer and remains first choice. It remains to be seen whether Iván Villar will leave the club altogether or stay on as third-choice goalkeeper once Bayindir arrives.
With Aleix Febas and Javi Galán already signed, and the arrival of Senegalese centre-back Abdoulaye Faye from Bayer Leverkusen also close to completion, Celta would have only an attacking player left to add to complete their squad rebuild.
Both Bayindir and Faye are expected to be with the squad in Italy next week. Celta's technical secretariat also remains busy on the outgoing side of the ledger, working to move on players such as Unai Núñez and Carlos Domínguez before the transfer window closes and the squad is finalised for the new campaign.
Bayindir's departure, meanwhile, continues Manchester United's push to trim their goalkeeping department and reduce their wage bill after a frustrating spell in England behind Onana in the pecking order.