(Theoretical) Paying credit cards with other credit cards
A "balance transfer" is paying one credit card with another.  You probably get offers in the mail to do this all of the time.  As other posters have noted, however, this usually comes with finance fees rather than the rewards that you get for normal purchases because it's written into your credit card agreement as a different class of transaction with different rules. I'm not sure if it's urban legend or true, but I have heard stories that suggest there were some "loop holes" in the earliest credit card reward plans that allowed for something like what you want.  I doubt that any plan ever allowed exactly what you've written, but I've heard stories about people buying gift cards from merchants and then using the gift cards to pay their bill.  This loop hole (if it ever existed) is closed now, but it would have allowed for essentially infinite generation of rewards at no cost to the cardholder.  The banks and credit card companies have a lot of years of experience at this sort of thing now, so the threshold for you finding something that works and conforms with the cardholder agreement is pretty small.