Legally Create Mononym (Single Name) on Facebook
In general condition, Facebook do not allow mononym but if you have only single name in your ID, you can request a mononym by filling out a form legally.
If you are a existing user of Facebook and you have existing account, to change your full name into mononym click this form. If you are trying to register new account using single name you can fill out this form.
In these both form there are two row to fill out first and last name. You should input the same name for both new first name and new last name.
Keep in mind that to create mononym, your name must match the government issued ID you submitted
If you don’t have such a identity, you can still create single name (mononym) To create click here