The building society said life-saving training will also be offered to staff and communities.
Nationwide Building Society is installing defibrillators and bleed control kits across its 605 branches.
The rollout, which will see the kits installed from now until the end of the year, is in partnership with Visa.
St John Ambulance is also working alongside Nationwide to offer life-saving training to 4,000 members of staff as well as local communities.
Nationwide has previously promised to keep all branches open until at least 2030.
Amanda Beech, Nationwide’s director of retail services, said: “By transforming our branches into visible, emergency hubs, we’re making it easier to access help when every second counts.
“Crucially we’re also offering training to all our branch colleagues, before extending that training into the communities we serve.
“We want more people to feel prepared, confident and ready to act when it matters most.”
St John Ambulance chief medical officer Professor Andrew Hartle said: “We’re so pleased to work with Nationwide and Visa on this project, which so perfectly meets St John Ambulance’s mission to put the power of first aid into everyone’s hands.
“With hundreds more public access defibrillators and bleed control kits across the UK, and thousands more people confident to use them, I am confident many more lives will be saved in our communities.”
Nationwide said a rollout of the initiative will also follow in Virgin Money branches.
