GoKawiilWhatsApp is set to let people chat without having to reveal their phone number - by exchanging unique usernames instead.
It will be rolled out globally to the platform's three billion account holders over the next few months, the platform said.
From Monday, users will start being able to reserve a name via the app, although it will not be compulsory.
The firm said people would be able to remove or change their usernames at any time.
Once it is fully activated, WhatsApp users will be able to connect after exchanging usernames only. There will still be options to block or report unwanted messages.
Names will be limited to 35 characters and there will be few restrictions, with the exception of some high profile officials and celebrities whose names will not be made available to anyone else.
So it's unlikely WhatsApp will be overrun with users calling themselves Donald Trump, for example.
The Meta-owned firm described usernames as a privacy feature.
Alice Newton-Rex, WhatsApp's head of product, said she had heard from users that they didn't always want to share their phone numbers in order to be in contact with others, particularly in group chats.
She said she hoped the feature would "give users control over how they choose to show up" on the app.