Sometimes is desirable that not just anyone can register as a user for the website. You can prevent new user registrations by following these steps:
Login to your WordPress website.
Navigate to Settings > General.
In the Membership section, make sure that the checkbox is empty for "Anyone can register".
Save your changes from the button below, and you are done.
How to Prevent Spam Registrations
Spam registrations on WordPress site can be prevented by activating reCaptcha on the registration form.

