How to Untag on Facebook with the iPhoneby Isobel Phillips
When someone tags you on Facebook in a post or photo, they create a link to your Timeline that may be visible to their friends as well as yours. Tagging may be used to draw your attention to a photo that you don't appear in and, depending on your privacy settings, post it on your Timeline. You can choose to be notified when someone tags you and a tag from someone you're not friends with may be held until you review it. You can untag photos -- but not posts -- from the iPhone app.
Log in to your Facebook account from the iPhone application and locate the photo you want to untag.
Tap the photo to open it in a new screen.
Tap on the three dots under the photo and on the next screen select "Report Photo."
Tap "I want to untag myself" and press "Continue." Tap "OK" on the next screen to confirm.