How do I perform a factory reset on my Samsung Galaxy S III?

Follow the steps below:

* Please backup your data before Factory Reset using Kies on your computer. App data is not backed up automatically.

1. From the Home screen touch Apps.
2. Touch Settings.
3. Touch the Accounts tab.

4. Touch Back up and reset
5. Touch Factory data reset
6. Touch Reset phone.
7. Touch Erase everything.

Performing a settings reset will delete all your personal settings including any changes you have made to your profile or wallpaper.

You may also lose any messages you have on the phone, all contacts if these have not been backed up to the SIM card or your Google account, and any apps that you have downloaded.