Customers and staff at a bank who do not identify themselves with being specifically male or female will now be able to choose non-binary as an option when filling out forms.
Metro Bank said the option will be available to customers taking out products, such as current accounts, with the bank, and members of staff joining up.
As well as choosing options like Mr, Mrs or Miss, customers and staff will also now be able to opt for Mx when giving their title.
Metro Bank said it has made the changes in response to feedback from staff and customers and as a relatively new bank it was able to react quickly.
Danny Hamer, Metro Bank's chief people officer, said: "Making sure our customers and colleagues feel comfortable and accepted is a real priority for us, that's why we listened and acted on the feedback we received.
"We hope that today's announcement will help encourage others to follow in our footsteps."