Answer
If you still have access to your account, you can find your username in your personal profile. When you open your profile, you will see it displayed directly under your full name. You can also find the user name via "Personal information".
If have forgotten your username, you can also look for the first e-mail you received from us when you opened your account. This email is entitled "Welcome to DEGIRO" and contains your username.
However, if you no longer have access to your account and cannot find the welcome e-mail, please contact our Service Desk by phone.