What is the ruling on bank interest in Islam, and is it forbidden or permissible?

The ruling on interest from usurious banks is prohibition, because it is usury. Allah, the Almighty, says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal - [thus] you do no wrong, nor are you wronged."