How to disable that “Guest User” from appearing at the OS X 10.8.5 login screen
How to disable that “Guest User” from appearing at the OS X login screen

For modern versions of OS X, disabling Guest account is done as follows:    (I have provided a screenshot from El Capitan, but Yosemite is very similar)



Open System Preferences
Go to “Users &amp; Groups” and click the unlock icon
Click on “Guest User”
Uncheck the box for ‘Allow guests to log in to this computer’ 



The key here is everything must be disabled.  Once you completely disable the account, it will no longer show up on the login screen.

If you have older versions of OS X, follow the instructions below:

Disabling Guest User in OS X Lion, Mountain Lion


Click on “Security &amp; Privacy”
Click the lock in the lower corner and type in your administrative
password to unlock the control panel
Check the box next to “Disable restarting to Safari when screen is
locked”