transparent UITextView

In Xcode 4 use interface builder and choose Background as Default

Up to iOS 4.3 You had to do the Interface Builder version of setting the background opacity. But as of iOS 5, you can set the backgroundColor and it will work. Just keep in mind when making apps for older OS versions.

Change background color, and use opacity slider to make it fully transparent.

Programmatically:

textView.backgroundColor = [UIColor clearColor];