Southgate said: "I am really pleased Tom has agreed to join us in Germany. Experience tells us that a tournament can put a lot of demand on our goalkeeping group led by Martyn Margetson. Tom will play an invaluable role on the training pitch supporting Jordan, Aaron and Dean.
"Off the field as someone we all know well, he will add to the positive environment we are always looking to create. We are grateful to Manchester United for their support in making this happen."
Heaton wrote on X: "Incredibly honoured to be asked by Gareth to join the squad. To get the call to go to a major tournament, to help in anyway I can and pass on my experience is a proud moment We have a great squad, I’m excited and can't wait to join the group."