Yes. You can change your display name in the profile settings.
Go to Account and Profile - Account - Account Settings in the left-hand menu, or use the shortcut in the profile dropdown top right. Your display name is shown as "Profile Name" in the settings form. Edit it and click "Save changes'. The new name will be shown throughout the site immediately.
Note: your display name is different from your username. The username is used for login and is harder to change (see the article about changing your username). The display name is just what other users see next to your content.