Is it possible to change my Jagex account username?

Yes, it is possible to change your Jagex account username. Jagex offers a one-time username change for all accounts. To request a change, you need to log in to your account on the official Jagex website and go to the Account Management section. In the Account Settings page, you will find an option to change your display name. Click on it and follow the instructions to select a new username. It's important to note that the requested username must be available and can't be already in use by another account. Additionally, changing your username may reset some of your in-game settings and achievements, so make sure to read the guidelines provided by Jagex before proceeding with the change.